Conceptually it is a particular type of convention, from the doctrinal construction of Roman republican law; the classical Roman doctrine refined its definition and has been integrated into practically all Western (not to say global) legal architectures; Obviously, there are some nuances that are not of interest to refer to now, although it is related to the fact that, in essence, the legal construction of a contract must be understood as a particular form of convention. Thus, in the Digest of Justinian, the following definition of convention is authored by Ulpian: “Conventio (est) duorum, vel plurium in idem placitum consensus de dar aliquo, fazando, vel praestando” [the convention is the consent of two or more people who agree on something, which they must give or do], which must be complemented with the Roman doctrinal definition of contract, as follows: "contractus (est) conventio quae habet vel nomen, vel causam” [the contract is the convention that has either a name or a cause]. The Latin literal is explicit. As a result of the codification that occurred during the century in Europe, the synthetic definition of contract as a convention was incorporated into the bodies of the different national civil law, without it being considered as any novelty, since the Justinian Code did not cease to be applicable law, directly or by incorporation into other national repertoires, since before the different modern law codes. Therefore, it should not be understood, under any circumstances, as a creation of French or Napoleonic law; not even in the literal meaning of the expression, as demonstrated by the original source of the Digest.

Most of the civil codes of countries whose legal systems historically come from the Roman-canonical and Germanic system, contain approximate definitions of contract. Most of them follow the structural guidelines of the French Civil Code, heir to the Napoleonic Code, whose article 1101 establishes (repeating the literal of the Digest referred to above) that the contract is the convention by which one or more people bind themselves, with another or others, to give, do, or not do something.

The German Civil Code prescribes that "for the formation of a binding transaction by legal acts, as for any modification of the content of a binding transaction, a contract concluded between the parties is required, unless the law provides otherwise." For its part, the Swiss Civil Code states that "there is a contract if the parties manifest their reciprocal will in a concordant manner; this manifestation may be express or tacit."

The Civil Code of the former Soviet Union only stated that "legal acts, that is, acts that tend to establish, modify or extinguish civil law relations, may be unilateral or bilateral (contracts)."

The Spanish Civil Code, in its art. 1254, like all those in continental Europe, also follows the trail marked by the Corpus Iuris Civilis of Justinian, as it could not be otherwise according to the sources of Castilian or Aragonese law, adhering to its own tradition; However, the codification work throughout the century in Spain adjusted, among other compilations, to the systematics of the Napoleonic Code. By direct influence of the Digest, the rule is expressed as follows: "the contract exists when one or more people agree to bind themselves, with respect to another or others, to give something or provide some service."[6]​

The Argentine Civil Code, in its art. 1137, establishes that "there is a contract when several people agree on a declaration of common will, intended to regulate their rights."[7]​.

According to the Civil Code of Uruguay (art. 1247), "Contract is an agreement by which one party is obligated to the other or both parties are reciprocally obligated to provide any service, that is, to give, do or not do something."

Influenced by the evolution of civil law in South America, in the Republic of Ecuador in a similar sense it prescribes as a contract in art. 1454 "Contract or convention is an act by which one party is obliged to another to give, do or not do something. Each can be one or many people."

The Civil Code of Bolivia (art. 450) indicates, “There is a contract when two or more people agree to establish, modify or extinguish a legal relationship between themselves.”

In El Salvador, its Civil Code (art. 1309) defines it as “Contract is an agreement by virtue of which one or more people are obligated towards another or others, or reciprocally, to give, do or not do something.”

Contenido

De entre los antecedentes remotos, sobre los que hay mayor grado de coincidencia en la doctrina, pueden citarse los siguientes:.

Roman contractual system

In Roman Law the contract appears as a form of agreement (conventio). The convention is the consent of two or more people who agree on something that they must give or lend. Consensuality was the dominant prototype.

The convention is divided into a pact (pactum) and a contract (contractus), the pact being that which has no name or cause and the contract being that which has one. In this context, a name is understood as the word that produces the action (the pact refers only to relationships that only generate an exception). The cause is some present thing from which the obligation is derived. The pact was gradually assimilated to the contract as actions were considered the instrument to demand compliance.

The contract applies to any agreement of wills aimed at creating civilly enforceable obligations and was always protected by an action that gave it full legal effectiveness.

Contracts are divided into true and quasi-contracts. Those that were based on the express consent of the parties were true and those based on the presumptive consent were quasi-contracts.

In turn, true contracts were divided into nominated and innominated. Nominated were those who had a specific and particular name confirmed by law (e.g. sale) and unnominated were those who, even though they had a cause, did not have a name. There were four unnamed contracts: "I give so that you give", "I give so that you do", "I do so that you give" and "I do so that you do". The characteristic of unnamed contracts is that they did not involve counted money.

In Roman Law there were unilateral and bilateral contracts. Unilateral contracts were binding on only one of the parties (for example, mutual contracts) and bilateral contracts were binding on both parties (as in the case of sale).

The action (Actio) was the other essential element of contracts in Roman Law. Actions relating to contracts are actiones in personam in which the plaintiff bases his claim on a contractual or criminal obligation, which could be Direct and Contrary. Examples of them are:

• - "Actio direct": Direct actions were those that the creditor had, against the debtor, from the moment of the conclusion of the contract, such as. the "actio certi" (which pursues a specific object, sum of money or thing); the "actio ex stipulatio" (which the creditor has when the object was neither money nor generic goods but rather involved an action); the “actio locati” (that the landlord has against the tenant); the “actio commodati direct” (to achieve the restitution of the thing loaned); the “actio depositi direct” (to demand from the depositary the return of the deposited thing); the “actio mandati direct” (to hold the agent accountable for the mandate); the “actio pledgeoraticia direct” (for the owner to recover the thing pledged); the “actio negotiorum Gestiónrum Directa” (to demand accountability from the manager of a business).

• - "Actio Contraria": Actions for which compensation is always requested, that is, they arise after the contract has been made, such as the "actio fiduciae" (for the return of the property transferred as collateral); the “actio redhibitoria” (to terminate the contract if hidden defects are found in the thing sold); the "actio quanti minoris" (by which the buyer demands a reduction in the price of the thing because it does not correspond to the real price), the latter also called "actio estimatoria"; the "actio conducti" (to enforce the lessor's obligations); the "actio commodati contrara" (to obtain compensation for possible damages or expenses caused by the thing given in bailment that has been caused to the bailor; the "actio depositi contrari" (for the depositor to pay the costs of the deposit); the "actio mandati contra" (to demand that the principal accounts for the expenses incurred during the mandate); the "actio pledgeaticia contrasta" (for the pledgee to demand recovery of the damages and expenses caused by the pledged thing); the “actio aerviana” (which allowed the pledger to remain in possession of the invecta et illata that were to serve as collateral); "actio depensi" (for the guarantor to collect from the principal debtor what had not been reimbursed); the "actio poenae persecutoria" (for the reparation of damage); "actio civilis incerti" or "civilis in factum", typical of unnamed contracts; and "actio doli" (criminal action taken against someone who damages with intent).

Some types of contracts in Roman law were:

• - Aestimatum. Contract under which a party receives appraised objects with the obligation to sell or return them after a certain time.

• - Chirographum. Way of being obligated by pilgrims, by virtue of which the debtor gave the creditor a receipt.

• - Syngraphae. Literal way for pilgrims to bind themselves, consisting of two copies, one in the power of the creditor and the other in the power of the debtor.

• - Conventio in manum: Contract verbis by virtue of which when a woman marries, she enters her husband's family, legally occupying the place of a daughter.

• - Depositum: Deposit. Contract that is perfected "Perfection (Law)") with the delivery of the thing that the depositary must return when the depositor requires it.

• - Depositum irregulare: Deposit of money or fungible goods.

• - Dictio dotis. Verbis contract in which the father, a third party or the woman undertake to constitute a dowry.

• - Iusiurandum liberti: Contract verbis by virtue of which the slave undertakes to provide certain services to the master. Also called promissio iurata liberti.

• - Locatio conductio: Lease. One of the parties (locator) undertakes to procure for the other (conductor) the temporary use and enjoyment of a thing or the provision of a certain service (locatio conductio operanum) or the execution of a work (locatio conductio operis), in exchange for an amount of money called merces.

• - Mandatum: Mandate. Contract by virtue of which one person (principal) entrusts another (agent) with the free performance of a certain act, for the account or interest of that person or third party.

• - Pignus: Garment. The debtor, or a third party, delivers possession of a thing to the creditor, as collateral for a debt.

• - Precarium: Unnamed contract by which one of the parties grants the loan of something to the other party, who has specifically requested it (preces) and who is obliged to return it upon the first request.

• - Societas: Society. Contract between two or more people, in order to participate in profits and losses.

• - Stipulatio: Verbal, solemn, unilateral contract stipulation that consists of a question followed by a consistent answer.

• - Transactio: Unnamed contract that consists of an extrajudicial agreement by virtue of which the parties make concessions to avoid the results of the subsequent trial.

Contracts typified in the Seven Items

The Code of the Siete Partidas of King Alfonso The Fifth Part, composed of 15 titles and 374 laws, refers to the acts and contracts that human beings can carry out or celebrate in the course of their life (private law). It deals with the mutual contract, prohibiting the collection of interest or "usury"; of bailment; deposit "Deposit (contract)"); of donation; of sale, with the distinction between title and mode of acquisition (from Roman law); exchange; rental or leasing; of company or partnership; of stipulation or promise; and the bail and the peños (mortgages and pledges "Pledge (rem)")).

It also refers to the payment and transfer of assets. Likewise, it includes important rules of commercial law, referring to merchants and commercial contracts.

Interpretar un texto consiste en atribuir significado preciso a sus palabras. La interpretación de cualquier texto es fundamental, y especialmente lo es en materia de contratos, porque de ella depende la posterior calificación jurídica y determinación de los efectos que el ordenamiento asigna a la manifestación de la voluntad comprendida en sus términos. Tratándose de los contratos su interpretación tendrá en esencia que definir la causa, el objeto y las manifestaciones de voluntad con integración de aquello que, no siendo esencial, falte a su perfección (principio de integración del contrato). El problema de la incoherencia del contrato, en caso de discordia entre las partes, se traslada al juez, que aplicará las reglas interpretativas conforme al principio de legalidad.[8]​.

Interpretation methods

There are several methods of interpretation that may vary depending on the civil code that governs.

But basically two currents are observed, two methods of interpretation: the one that proposes to analyze the text (literally) and the one that proposes to find the common intention of the parties, that is, what the authors wanted to say. Several authors understand that getting to know the common will of the parties is very complex and increases the discretion of the judge.

According to this theory, the judge must seek the solution based on the intentions that the parties had at the time of contracting. The judge's job would then consist of investigating these intentions. It is the option followed, among others, by the Chilean Civil Code (art. 1560) and the Spanish one (arts. 1281 and 1286).

The judge must evaluate the objective data that emanate from the agreement to specify what the common intention of the parties was. It is the option followed, for example, by the French Civil Code and that of Mexico City.[9]​.

Guidelines for the interpretation of ambiguous expressions

Clauses susceptible to two meanings, in one meaning the validity and in the other the nullity of the act, must be understood in the first one.

Equivocal or ambiguous clauses must be interpreted through the clear and precise terms used elsewhere in the same writing.

The facts of the contracting parties, subsequent to the contract, that are related to what is discussed, will serve to explain the intention of the parties at the time of entering into the contract.

Ambiguous clauses are interpreted by what is customary and customary in the place of contract.

Interpretation in favor of the debtor

Ambiguous clauses must be interpreted in favor of the debtor (favor debitoris). But ambiguous or obscure clauses that have been extended or dictated by one of the parties, whether creditor or debtor, will be interpreted against it, provided that the ambiguity comes from its lack of explanation. The above reflects an ancient Roman rule (interpretatio contra stipulator), its foundation is found in the principle of responsibility, which imposes the burden of speaking clearly. Thus the obscurity of the pact must harm the declarant. The generality of consumer protection laws establish that when in doubt it must be interpreted in favor of the consumer.

Theory of unpredictability

The theory of unpredictability also applies to contracts, in the event that, due to radical changes in general economic conditions, the satisfaction of the contract becomes excessively burdensome, and the conditions of the contract must be adjusted so that they resemble what the parties originally had in mind.

Se trata aquí de analizar aquellos actos, causas, hechos, requisitos y formas que, instantánea o sucesivamente, han de confluir para la perfección y cumplimiento del contrato.

agreement of wills

The contract requires the unequivocal manifestation of the will of the parties that will form the legal act. Thus, when the contracting parties express their will at the time the contract is formed, it is called between presents. When the manifestation of will occurs at different times, it is called between absentees. The distinction is important to be able to determine exactly the moment in which the contract enters the legal life of the contracting parties. The contract between those present will come into force at the time of the simultaneous expression of the will, while the contract between those absent only until the last contracting party has given his expression.

Offer and acceptance

• - The offer is a unilateral manifestation of will, directed to another. The classic example is that of a retailer that offers its products to anyone, at a certain price. The offer is mandatory, that is, once issued, the proposer cannot modify it at the time of acceptance by the interested party.

• - The acceptance of the offer must be explicit, so that the other contracting party must show its express or tacit consent, in a way that indicates its unequivocal intention to accept the offer and adhere to the offeror's conditions.

The mandatory validity of the offer varies in different legal systems. For some, the offeror can vary the offer as long as it has not been accepted; However, in others the offer must remain intact for the entire period that, usually or legally, the contracting party is recognized to accept it.

Acceptance in the contract between absent/distant persons

There are various theories regarding the moment in which a contract develops its legal effects when it involves parties that are physically distanced from each other. Various theories come together:

• - Issue theory: It understands that the offer is accepted at the moment the acceptor accepts it.

• - Remission (or issuance) theory: Acceptance occurs at the moment it is accepted and remission of said acceptance is given to the offeror.

• - Reception theory: Acceptance would occur in this case after acceptance, referral and arrival of the latter to the area where the offeror carries out its activity (company, home, etc.).

• - Theory of knowledge: Requires acceptance, referral, arrival in the field and, in addition, knowledge of it. Spanish doctrine leans towards the theory of reception, despite the fact that the theory of knowledge is stricter (see jurisprudence on the matter, or the Automatic Contracting Law).

Pre-contractual stage

The purpose of the pre-contract is the preparation of a future contract. Three different types of pre-contract can be identified:

• - The contrahendo pact. People bind each other to carry out negotiations that result in a future contract. They cannot arbitrarily break off negotiations without incurring contractual liability.

• - The accepted unilateral promise. A subject presents an offer for a future contract to another subject, who agrees to study it and decide whether to accept or reject it. The offeror agrees not to withdraw the offer during a certain period. Only the offeror is bound by this agreement. Commercial proposals are a typical example of this type of pre-contract, where the offering company agrees to keep the offer intact for a certain period, for example, 30 days.

• - The bilateral or reciprocal promise.

El contrato tiene todos los elementos y requisitos propios de un acto jurídico que son los elementos personales, elementos reales y elementos formales.

Essential elements

There are basically three requirements that, in almost all legal systems, the laws require to achieve the effectiveness of the contract: consent, object and cause.

It is the volitional element, the internal will, the will that, manifested under consent, produces legal effects. The perfection of the contract requires that consent be freely given by all the parties involved, due to or effect of the principle of relativity of contracts. The will is expressed by the successive concurrence of the offer and acceptance"), in relation to the thing and the cause that must constitute the contract. Vitiated consent will be void, for having been given by mistake, with violence or intimidation, or fraud, or by a subject other than the object of the contract.

The absence of defects in the consent is essential for the validity and effectiveness of the contract, to which end it is required that the will not be pressured by external factors that modify the true intention. The most prominent vices of consent are: (a) error, (b) violence and (c) fraud.

• - (a) The error: When the error refers, there is a mistake about the object of the contract, or about some of its essential aspects. The error is a reason for nullity of the contract when it falls on the nature of the contract (he wanted to make a lease and made a sale), on the identity of the object, or on the specific qualities of the thing.

The error must not be in bad faith, because otherwise, it becomes fraud.

• - (b) Force or violence: In violence, an irresistible force is exerted that causes serious fear to one of the parties to the contract, or that one of the parties has abused the weakness of the other. The threat of going before a judicial authority to claim a right is not coercion, unless this right is abusively threatened.

• - (c) Fraud: Any artificial, fraudulent or contrary to good faith means, used with the purpose of deceiving, or confusing, to induce a person to consent to a contract that, if they had known the truth, they would not have accepted it, is considered fraud. The victim of fraud can maintain the contract and claim damages.

All things "Thing (Right)") that are not outside the commerce of men, even future things, can be the object of contracts. All services "Service (economy)") that are not contrary to laws, morality, good customs or public order may also be the subject of a contract.

Normally, the civil regulations of legal systems require that there be a just cause for the birth of legal acts. The cause is the determining reason that led the parties to enter into the contract.

A contract has no cause when the manifestations of will do not correspond to the social function that it must fulfill, nor when a cause is simulated or feigned. The contract must have a cause and this must be existing, true and lawful.

• - Source cause: it is the origin or legal fact that generates obligations or a legal act.

• - Purpose: it is the purpose or purpose pursued by the parties when carrying out the legal act or business.

The problem of cause revolves around the 'final cause'. There have been disagreements and debates that still remain active about whether the final cause should be considered an essential element of legal acts. Apparently due to the wording of Art. 944 of the CC it should be. For those who consider that the final cause should not be part of the essential elements of the legal act, they express that it is confused with its object or with its consent. This position affirms that the essential elements of business are: subject, object and form. But for those who consider that the final cause is part of the legal business, they distinguish:

• - The object: as the matter on which the legal act deals, that is, the facts, the things (marketable things, services to be provided, current or future: with what is going to be done) and;.

• - The cause: as the purpose taken into account or in view by the parties when entering into the transaction (origin or legal fact generating obligations: what they want to do and who will be obliged).

• - Difficulty of the subject.

• - Appearance of the problem of cause in the field of law.

Jean Domat was the first to develop the causalist theory of obligations; he maintained that the cause of obligations resided in the consideration exercised by one person in relation to another. His doctrine was followed and disseminated by his disciple Robert-Joseph Pothier, and was later included in the French Civil Code of 1804. These causalists distinguished synallagmatic contracts from real, unilateral contracts and those with free titles. Domat and Pothier required as an element for the validity of a contract "a lawful cause in the obligation."

When the French doctrine of causalism was at its peak"), in 1826 an essay by the Belgian A.-N.-J. Ernst appears, entitled "The cause is an essential element of the contractual obligation." different elements and require four conditions: will, capacity, object and cause, when in reality there are only three. If in gratuitous contracts the cause resides in the freedom of the benefactor, it is also not true that this is in itself an external condition of the existence of such contracts. A feeling that animates the donor cannot be separated from the will that she expresses, to make it an element of the contract.

Planiol affirms that: "The cause is false and useless." It is false because if it is said that in bilateral contracts the cause of the obligation of one of the parties is the performance of the other, it forgets that the performance and the obligation arise at the same time and it is not possible for one thing to be the cause of the other. Most French and European causalists have turned to these theories.

At the end of the century and the beginning of the century, neocausalists have appeared. Indeed, Henri Capitant"), Jacques Maury") and Louis Josserand have revived the theories of Domat and Pothier. The neocausalists were objectivists, they maintained that the cause element is essentially a psychological factor, they conceive the cause as the concrete end, the purpose, the interest that induces the parties to contract, the immediate and determining end that they have had in mind. There is no will without an interest. Modern codes have eliminated the cause in their legislation, others have incorporated it, but there is a marked interest in eliminating it from current codes.

In general terms we can affirm that the Argentine Civil Code alludes to the cause, in its art. 417, when it provides that: The obligations derive from any of the sources established by law. As can be seen, this article incorporates a causalist notion of obligations. Now, when we talk about the cause in the new code, it can be said that practically nothing has changed in relation to its predecessor, we are referring to the Vélez Sarfield code.

Personal items

The subjects of the contract may be natural persons (individuals) or legal entities, with the capacity to act legally, necessary to be bound. In this sense, capacity in law is subdivided into capacity to enjoy (the legal capacity to be the holder of subjective rights, commonly also known as legal capacity) and capacity to exercise or act, active or passive (legal capacity to exercise rights and contract obligations without assistance or representation from third parties, also known as capacity to act).

real elements

They integrate the so-called performance and consideration, that is, the thing or service that is the object of the contract, on the one hand, and the delivery of a sum of money in exchange for it, or another agreement, on the other.

Formal elements

The form is the set of signs by which the consent of the parties is expressed in the conclusion of a contract. Some contracts may require a specific form of conclusion. For example, the written form may be necessary, the signature before a notary or before a notary and before witnesses, etc. In the case of written form, the document may include the following sections: background or recitals, declarations and clauses.

Accidental elements

They are those that the parties establish through special clauses, which are not contrary to the law, morality, good customs, or public order. For example: the term, the condition "Condition (Law)"), the mode "Mode (law)"), solidarity, indivisibility, representation, etc.

In accordance with the autonomy of the will, the contracting parties can establish the agreements, clauses and conditions that they deem appropriate, as long as they are not contrary to the law, morality, good practices and customs, or public order.

The form can be decisive, sometimes, of the validity and effectiveness of the contracts. Contracts can be verbal or written; verbal, if its content is preserved only in the memory of the participants, or written, if its content has been transformed into grammatical text reflected or recorded on a permanent and durable medium (paper, visual or sound magnetic tape, CD, DVD, PD, etc.) that allows its reading and exact subsequent reproduction.

Contracts that are in electronic or digital form (those that are not signed on paper) have the same validity as any other contract as indicated in the UNCITRAL Model Law on electronic commerce in its articles 5 and 11.[11]​.

Written contracts can also be solemn or not, depending on whether they must be formalized in a notarized public deed, and even if the law requires their registration in some type of public registry (Property Registry, Commercial Registry, Registry of cooperatives, Registry of collaborating urban planning entities, etc.). In so-called real contracts, the perfection of their form also requires the delivery of the thing (for example, the loan, even if it is recorded in a public deed, does not arise if the capital "Capital (finance)" lent is not delivered in the act of signing the contract).

In some States of the European Union there is regulation on the font size of contracts with consumers (e.g. Spain, France, Portugal).

The font size of the contracts is a validity requirement that is included in the accessibility and legibility of the general contracting conditions with consumers. In Spain it is regulated in article 80.1.b) of the Consolidated Text of the General Law of Consumers and Users.[12] If the letter does not have the established minimum legal size, the contract or the general condition without the legal size is null or there is no so-called "incorporation" of the general condition.

The font size of contracts is usually regulated in typographical point and/or in millimeters. To understand the equivalence, the convention is that a 1 Typographic Point is equivalent to 0.3527mm*.* In Spain the font size of the contract may not be less than 2.5 millimeters (equivalent to a size 7 in Typographic Point,[13]​ according to the equivalence 1 Typographic Point = 0.3527mm) from June 1, 2022; Until that date arrives, the minimum font size is 1.5 millimeters.

Citamos, a continuación, las clases más comunes, sobre las cuales la doctrina es coincidente, y que son:.

Unilateral and bilateral contracts

• - Unilateral contract: it is an agreement of wills that generates obligations only for one party.

• - Bilateral contract: it is the agreement of wills that gives rise to obligations for both parties.

• - Multi-party contract: it is the agreement of wills that gives rise to contracts between two or more parties (e.g.: in the Civil Code of Colombia, Art. 507. Definition of Participation Accounts. Participation is a contract by which two or more people... ommisis.), for which it is assumed to be multi-parties.

• - When in a unilateral contract there are obligations that imply the transfer of something, if it is destroyed by chance or force majeure it is necessary to be able to establish who should suffer the loss. The thing always perishes for the creditor (in transfer contracts of ownership the creditor is the owner; while in transfer contracts of use, the creditor for restitution is the owner and the thing perishes for him). If the contract were bilateral, there would be no possibility of raising the problem, because this issue assumes that since the obligations are reciprocal, one party does not comply by delivering the thing, due to a case of force majeure and in view of this the other party must comply, since the debtor's non-compliance is not attributable.

• - The exception of unfulfilled contract (exceptio non adimpleti). In all bilateral contracts, which generate reciprocal obligations, when one party does not comply or agrees to comply, it lacks the right to demand that the other comply with its obligation, and if despite this it intends to judicially demand compliance by means of a lawsuit, the defendant will raise the exception of unfulfilled contract (principle "default (right) purges default"). The exceptio non adimpleti cannot be presented in unilateral contracts, for the simple reason that in them only one of the parties is obliged, and if it does not comply, the other may judicially demand compliance, without said exception being able to be opposed to it, since it has no obligation to perform on its part.

Onerous and free contracts

• - Onerous contract: it is one in which there are reciprocal benefits and encumbrances, in this there is an equivalent sacrifice made by the parties (equivalence in reciprocal benefits); for example, the sale, because the seller receives the benefit of the price and at the same time delivers the thing, and vice versa, the buyer receives the benefit of receiving the thing and the burden of paying.

• - Free contract: its purpose is only the utility of one of the two parties, with the other suffering the burden. Therefore, a contract in which the benefit is for only one of the parties is free, such as a bailment.

Commutative and random contracts

This classification only applies to bilateral contracts.

• - Commutative contract: is that contract in which the performances that the parties owe are certain from the moment the legal act is concluded, a very clear example is the contract for the sale of a house.

• - Random contracts: is one that arises when the benefit depends on a future and uncertain event and at the time of contracting, the profits or losses are not known until the moment this future event occurs. Examples are the harvest sale contract called "hope", betting, games, etc.

Among the common characteristics of random contracts are:

• - Uncertainty about the existence of an event, as in a bet, or about the time of realization of that event (when).

• - The opposition and not only the interdependence of benefits, because when uncertainty ceases, one of the parties necessarily wins and the other loses, and, furthermore, the measure of the gain of one of the parties is the measure of the loss of the other.

It is important to note that the Dictionary of the Spanish Language defines the term random, from the Latin aleatorius which means, typical of the game of dice, adj. Of or relating to the game of chance.

Main and accessory contracts

• - Main contract: is one that exists by itself, while the accessories are those that depend on a main contract. The accessories follow the fate of the main thing because the nullity or non-existence of the first ones, in turn, causes the nullity or non-existence of the accessory contract.

• - Accessory contracts: they are also called "guarantee contracts", because they are generally established to guarantee the fulfillment of an obligation that is considered primary, and this form of guarantee can be personal, such as bail, in which a person undertakes to pay for the debtor, if he does not do so; or real, such as the mortgage, the pledge "Pledge (real right)"), in which a real right is constituted over an alienable asset, to guarantee the fulfillment of an obligation and its preference in payment.

The rule that the accessory follows the fate of the main thing suffers in certain cases from exceptions, because the accessory contract could not exist without the principal contract being previously established; However, the Law presents us with cases where there may be a bond, pledge or mortgage, without there yet being a main obligation, as occurs when future or conditional obligations are guaranteed.

Instant and subsequent contracts

• - Instant contracts, or single contract, are those that are fulfilled at the same time they are celebrated, that is, their fulfillment is carried out in a single act.

• - Successive Contract Contract: is one in which the performance of the benefits is carried out in a specific period, and which, at the request of the parties, can be extended to satisfy their primary needs and these terms can be:

• (a)Continuous execution: single execution but without interruption.

• (b) Periodic execution: various services that are executed on established dates.

• (c) Intermittent execution: occurs when requested by the other party.

Characteristics of the executions are: The execution is autonomous from the others, so each act is autonomous. There is retroactivity for each legal act that is carried out. If an illegal element is present, what should be done is to cancel any service already provided.

Consensual and real contract

• - Consensual contract: as a general rule, the consent of the parties is sufficient to form the contract; Obligations arise as soon as the parties have agreed. The consent of the parties can be expressed in any way. However, it is necessary that the will to contract have a particular form, which allows its existence to be known through it. It is not the simple coexistence of two internal wills that constitutes the contract; It is necessary that these be manifested outside.

• - Real contract: it is concluded from the moment in which one of the parties has made to the other the tradition or delivery of the thing about which the contract relates.

Formal, solemn or non-solemn, and non-formal contract

• - Formal contract: is one in which the law orders that consent be expressed by a certain means for the contract to be valid. In the legislation, an eclectic or mixed system is accepted with respect to formalities, because in principle, the contract is considered to be consensual, and only when the legislator imposes a certain formality must it be complied with, because otherwise the act will be affected by nullity. For example, the purchase and sale of real estate that must be granted by public deed.

• - Solemn formal contract: is one that, in addition to the manifestation of consent by a specific means, requires certain rites stipulated by law to produce its own effects. Vg. Marriage and divorce

• The formalities will be ad probationem when they must be carried out in order to demonstrate the celebration of an act; It generally consists of carrying out the act before a notary or public official for this purpose.

• The formalities will be ad solemnitatem when the will of the parties, due to legal requirements, requires a particular formality without which the contract has no legal effectiveness.

The distinction between formal and solemn contracts lies in what refers to the sanction. The lack of form causes relative nullity, or failing that, unenforceability before third parties; the lack of solemnity causes nonexistence.

Private and public contract

This classification meets various criteria:

(1) According to advertising or professional intervention in the contract:.

• - Private contract: is the one made by the people involved in a contract with or without professional advice. It will have the same value as the public deed between the people who sign them and their successors.

• - Public contract: these are contracts authorized by public officials or employees, always within the scope of their powers, and have better evidentiary status. Notarial documents are those that have the greatest importance and within them mainly public deeds.

(2) According to the quality of the participating subjects:.

• - Private contract: is the one made between natural or legal persons, whether public or private, in which there is relative contractual equality, with no powers that one can impose on the other.

• - Public or administrative contract: is the one concluded between the State or a public body and a natural or legal person, where the first of them maintains a series of powers over the second, called exorbitant, which place the latter in subordination to the former.

(3) For its advertising:.

• - Public: when they are carried out under the authority of notaries or judges.

• - Private: are contracts granted by the contracting parties without the authorization or existence of a notary public, although they may have the presence of witnesses.

Nominated or typical and innominated or atypical contract

• - Nominated or typical contract: is that contract that is provided for and regulated by law. Therefore, in the absence of agreement between the parties, there are dispositive rules to which to resort. (Purchase, leases...).

• - Unnamed contract or atypical: it is one for which the law does not have a specific name, because its characteristics are not regulated by it. It can be a hybrid between several contracts or even a completely new one. To fill in gaps in the law or situations not foreseen by the parties in the contract, it is necessary to resort to the regulation of similar or analogous contracts.

It is important to mention that unnamed contracts are not those that are not provided for by the civil code, because all contracts are; They are simply those that are not expressly defined in its articles, although, without prejudice to the parties expressly defining them at the time of contracting, within the framework of their autonomy of will.

Contracts determined solely in their kind

They are those in which only mention is made of the quantity and quality of the object of the contract, for example: The sale of 100 metric tons of soybeans. As you can see, it is not indicating which soybeans are sold; In this case it must be assumed that the quality is average.

The number of contract types that a legal system that has freedom of contract can offer is unlimited, as are the rights and obligations that the parties can create are almost infinite, including doing so in a pure and simple manner, or subject to some modality. However, the civil legislation of most countries has regulated the most important of these, either in their respective civil codes, or in special laws, creating a system of typical contracts or nominated, whose essential regulation appears in the laws and is removed from the parties of the contract, for the purposes of security, protection and balance between the possible subjects. The "typicality of contracts" is made effective through the "principle of contract integration", applied either in accordance with the formulation that the parties have attributed to their contract, or as deduced from the content of the clauses of the text, if the terms in which the contract has been formulated by the parties are unclear.

Effects between the parties

"The contract is law between the parties" is a common expression (contractus lex). However, this does not mean that contracts have power equivalent to that of laws. The fundamental precepts arising from the contracts, which the parties involved must observe, will be the following:

The parties must comply with the conditions stipulated in the contract (principle of literality).

The conditions and effects of the contract only have effect between the parties who accepted the contract, and their successors in title (principle of relativity of the contract).

The agreements contained in the contracts must be executed in the terms that were signed.

The stipulations of typical contracts, which are contrary to the law, are considered not in place.

Legal provisions recognize the contract as a source of obligations. Contractual obligations are civil obligations, so the creditor can demand from the debtor the satisfaction of the debt as agreed. In the event that compliance with the object of the obligation is not possible, by equivalence, the creditor may demand compensation for damages. Once a contract has been validly created, it becomes inalienable, and the obligations originated by the valid contract cannot be modified unilaterally.

Effects on third parties

In principle, contracts only have effects between the parties that form it. However, there are contracts that do have effects on third parties "Third Party (right)"). A third party is a subject who did not participate in the formation of the contractual relationship, and who, therefore, did not express his/her will regarding the contract. It may even be that the third party did not even know of the existence of the agreement.

(a) Effects regarding successors.- The affirmation that contracts bind heirs will fundamentally depend on the notion of succession that is handled in the legal system in which the opinion is issued. Thus, in legal systems such as the Costa Rican and Peruvian, confusion of assets does not operate, that is, the hereditary assets are responsible for the obligations of the deceased and not the assets of the heirs. On the other hand, in legal systems such as the Italian one, confusion of assets occurs, so the heirs respond even with their own assets for the obligations of their deceased (unless they accept with the benefit of inventory, if such an option exists).[14]​.

The nullity of the deceased's contracts after the succession affects the successors, as they may find themselves in the situation of having to return to third parties "Third Party (right)"). Additionally, individual successors in title will be affected by the restrictions imposed by the deceased, for example, a mortgage, an easement or a usufruct right in favor of another.

(b) Effects regarding unsecured creditors.- Any contract of the debtor that affects his assets implies a consequence for the guarantee of the unsecured creditor. To protect it, oblique action and Paulian action have been established, however, each of them can only be invoked under certain conditions. Namely, the oblique action can only be exercised by the creditor due to the debtor's inaction in protecting his own assets, and the Paulian action can only be exercised against a debtor who is in a state of insolvency.

(c) Effects regarding penitus extranei.- The penitus extranei are all those people outside a contractual relationship. Even so, the effects of the contracts are enforceable against these third parties, since they cannot claim ignorance of the legal act and its effects, as would be the case of real or personal rights registered in a public registry with legal effectiveness, marriage agreements, and the registrations of civil or commercial companies.

In principle, obligations cannot be assigned to subjects who have not participated and consented to the formation of the legal bond. But the case of the constitution of benefits in the name of third parties "Third Party (right)") is different.

Used as a method to obtain legal security, in a generic sense, the guarantee is one of the consequences of contracts, especially onerous transfers, insofar as its existence attributes to the parties the unquestionable power to acquire, occupy, demand or maintain the transferred real or personal right, wieldable both against the person who has transferred it, and against third parties, who must therefore cease pursuing the same object of the contract, so that, by its virtue, the subject can persist in enjoyment. peaceful benefit, or equity, obtained through the contract.

The most obvious "Proof (right)") of the contract protection system is found in the "remediation by eviction" and the "remediation due to hidden defects" to which the transferors are legally subject in a contract, a point of protection is created with which it is provided that in the event that the acquirer is stripped of the object due to a vindictive action by a subject with a better legal title (reipersecutoridad), the "guarantee for eviction" and the transferor must return not only the value of the thing, but also the legal expenses of the contract and the action taken to the contrary, if applicable. The same happens with the "hidden vices" of the transmitted good. So, one thing is the “guarantee of contracts” and another is the “guarantee contracts”. The latter in themselves contain the two virtues, that is, they are a generic guarantee of their content for the subjects who have signed them and they also contain, as part of their object, the merit of ensuring compliance with another contract or different obligation. Examples of the latter are guarantee contracts, comfort letter, stand-by letter, bond, pledge "Pledge (rem)"), mortgage, antichresis, insurance, etc.

Los principales elementos que concurren en un contrato de título oneroso son.

1. • La consolidación de la deuda. El contrato en sí mismo.

2. • La consolidación del instrumento de pago o de su efectivo ejercicio. Los elementos ejecutivos tangibles que dan a su valor residual exigible.

Caso contrario, se establece la duda razonable acerca del cumplimento efectivo del contrato, donde el acreedor es quien posee la carga de la prueba.

En la acción práctica del pago del deudor, es una función exclusiva y obligada por el acreedor dar fe de que el pago se ha realizado o se encuentra al corriente de pago, pero este jamás puede constituirse en juez y parte iudex et iudices ya que resulta ab absurdo esta posición, porque nunca puede decidir de manera imparcial como consecuencia de su propio interés. No puede ser el mismo acreedor quien determine la posición del deudor, situación que define un testis unus, testis nullus [testimonio único, testimonio nulo].

A título de ejemplo es el caso de cuando una entidad siendo parte del contrato a su vez resulta Juez en la determinación del pago.

Perfect debt consolidation and payment

There are two formulas to prevent the creditor from being judge and party, not committing a taint of partiality, and at the same time being able to demonstrate the existence of their creditor position of a total or partial debt in the signed contract.

1. • The imperative mediation of a third party, who receives the debtor's payments, to make them effective for the creditor. Therefore, this third party is the true witness who unequivocally gives independent and effective testimony to the parties of the state of partial or total compliance with the contract.

2. • The issuance of the respective documents (bills, promissory notes, etc.) that certify the payment as well as the capacity for collection by the creditor, when these are in their possession.

Any of these two elements are sufficient for the creditor to attest to the fulfillment of the debtor's obligations since the first interposes an independent witness and the second genuine instruments that in the debtor's possession legitimize and reliably accredit the amount owed.

From the legitimate intermediary

The intermediary who acts in a completely impartial manner by becoming a valid witness eliminates the presumption of testis unus, testis nullus, thus perfecting and certifying the creditor's argumentative validity in its entire scope.

From the collection instrument

In the absence of an impartial intermediary to accredit the operation, only the collection instrument survives as an element that perfects the enforcement procedure of the debt that the creditor wants to enforce.

In this way, all doubt about the debt is diluted and the creditor has all independent evidence without falling into the figure of "judge and party" which makes it impossible for him to be able to make the claim for a debt effective, since any settlement unilaterally prepared on his part, which does not have any legal force since the collection instrument becomes possessory constitution of the debt in question, because this obligation is accessory sequitur principale to the debt, among which There are collection instruments, unique for the effective accounting materialization of the payment ad probationem, which also establishes the existence of the remainder owed.

It is evident that the debtor has the power to alienate or simply destroy the proof(s) of these obligations so that they are not appropriated by third parties or due to the risk of falling into the hands of the creditor and the creditor is entitled to exercise the collection of said instrument.

There is no different way for the creditor to make a collection claim, in the absence of said instrumentation.

Uncertain computer qualification - Loss of Right by omission

The development of computing has left gaps in matters of law, imposing the technique as a validator of a Judicial process.

It is an erroneous condition to establish that the computer method is sufficient proof, as if it were an impartial third party intermediary. But it should not be forgotten that it is totally plausible to errors, but much more important is to consider that for the purposes of legal doctrine, it remains unilateral proof, although its processing speed and versatility are impressive.

Unfortunately, this is not the case, it does not perfect collection elements but rather leads to an irregular treatment of the law, when on the contrary, computer processing is precisely the ideal means to facilitate the issuance of collection instruments, simplifying this due to its automatic issuance.

Invalidity of credit execution due to lack of instruments

The legal truth is that the lack of the figure of the impartial intermediary as observer and its certification, as well as the lack of collection instruments, removes validity in natura from the collection certification, with the creditor intending to use only its own information and accounting entries, whether or not it is systematized in a computerized manner or by other means.

Under no circumstances, regardless of manual or technological means, can the creditor be the Judge and party to a process.

On the other hand, when in each payment the creditor delivers the promissory note or bill to the debtor, in this act the obligation of an installment, final payment, partial payment, etc. is extinguished. from the moment there is a contract that supports the obligation and the promissory note or letter that supports the veracity of the payment.

Formal execution

Since there is no impartial intermediary, the issuance of collection instruments is the only valid system, when it is the creditor who intends to execute a debt with a declaration presented in his judgment and value.

The consolidated debt is then simply the algebraic sum of the collection instruments in the creditor's (the creditor's) possession. The lack of existence of the collection documents terminates the obligation, canceling the debt and both parties have one.

Contractual liability is that which arises from the contract (unlike non-contractual liability) and requires that the party (subject) who demands it be linked by a contractual link to the person who owes it. The notion of non-compliance is widely debated in comparative law, however, it can be reduced to three main options.[15] Non-compliance is considered to be the non-verification tout court of the provision in its materiality, the non-achievement of the committed result and the specification of types of contractual infractions.

The choice of each of these options will incline the legal system to prefer a subjective or objective interpretation of liability.

Contracts are elements that are considered of "incomplete nature" given the difficulty of reflecting in them all possible contingencies.[16] In addition to this, contracts that lack any of the essential elements are ineffective, or even if these are present, they are nevertheless flawed in some way. Ineffectiveness has different manifestations and effects depending on the type of invalidity caused to the contract. In this regard, they are a consequence of typical disabling defects:

• - Voidability.

• - Nullity.

• - Resciliation.

• - Termination.

• - resolution.

• - revocation "Revocation (Right)").

• - Contract simulation.

• - Portal:Law. Content related to Law.

• - Quasi-contract.

• - Commercial contract.

• - Vices of the will.

• - Contract simulation.

• - Abusive clause.

• - Baudrit Carrillo, D.: Civil Law IV, Volume I. General Theory of Contract. 3rd edition, 2000.

• - Betancourt Serna, F.: Classical Roman Law. Ed. University of Seville. Publications Service. Seville, 2001 - ISBN 84-472-0614-9.

• - Brenes Córdoba, A.: Treatise on Contracts. 5th edition. 1998.

• - Castán Tobeñas, J.: Spanish civil law, common and regional. T-III. Law of obligations. The obligation and the contract in general. Reus Editorial. Madrid, 1977 - ISBN 84-290-1215-X, pp. 399 to 608.

• - Castán Tobeñas, J.: Spanish civil law, common and regional. T-IV. Law of obligations. The particular obligatory relationships. Reus Editorial. Madrid, 1977 - ISBN 84-290-1177-3.

• - Díez-Picazo and Ponce de León, L., and Gullón Ballesteros, A.: Civil Law System. Volume II.. General contract theory. The mandatory relationship in general. Obligatory relationships in particular. 1st edition. Tecnos Editorial. Madrid, 1977.

• - García Medina, J.: New and special forms of guarantee in commerce. Systematic and critical study. Ed. La Ley. Madrid, 2009 - ISBN 978-84-8126-209-4.

• - Kozolchyk, B.: Commercial contracting in Comparative Law. Ed. Dikynson. Madrid, 2006 - ISBN 84-9772-877-7.

• - Lasarte Álavarez, C.: Law of obligations. Principles of Civil Law II. Ed. Marcial Pons. Madrid, 2006.

• - Pérez Vargas, V.: Private Law. 3rd edition. Ed. Lehmann Bookstore. San José "San José (Costa Rica)"), 1994.

• - Ruiz Prieto, E.: Theory and characteristics of contracts according to the Civil Code[2], Ruiz Prieto Asesores Blog, 2016.

• - Ruiz Vadillo, E.: Civil law. Introduction to the theoretical-practical study. Ed. Ochoa. Logroño, 1987 - ISBN 84-7359-272-7 - pp. 305-361.

• - Stiglitz, Rubén: "Contracts. General Theory" (Director and author of Cátedra's collective work), Depalma, Bs. As., t. I, 1990 and t. II, 1993.

• - Stiglitz, Rubén: "Civil and commercial contracts. General theory", two volumes, Abeledo-Perrot, 1998/1999.

• - Contract | Legal Recourse. Page on conceptual issues of contracts.

Conceptually it is a particular type of convention, from the doctrinal construction of Roman republican law; the classical Roman doctrine refined its definition and has been integrated into practically all Western (not to say global) legal architectures; Obviously, there are some nuances that are not of interest to refer to now, although it is related to the fact that, in essence, the legal construction of a contract must be understood as a particular form of convention. Thus, in the Digest of Justinian, the following definition of convention is authored by Ulpian: “Conventio (est) duorum, vel plurium in idem placitum consensus de dar aliquo, fazando, vel praestando” [the convention is the consent of two or more people who agree on something, which they must give or do], which must be complemented with the Roman doctrinal definition of contract, as follows: "contractus (est) conventio quae habet vel nomen, vel causam” [the contract is the convention that has either a name or a cause]. The Latin literal is explicit. As a result of the codification that occurred during the century in Europe, the synthetic definition of contract as a convention was incorporated into the bodies of the different national civil law, without it being considered as any novelty, since the Justinian Code did not cease to be applicable law, directly or by incorporation into other national repertoires, since before the different modern law codes. Therefore, it should not be understood, under any circumstances, as a creation of French or Napoleonic law; not even in the literal meaning of the expression, as demonstrated by the original source of the Digest.

Most of the civil codes of countries whose legal systems historically come from the Roman-canonical and Germanic system, contain approximate definitions of contract. Most of them follow the structural guidelines of the French Civil Code, heir to the Napoleonic Code, whose article 1101 establishes (repeating the literal of the Digest referred to above) that the contract is the convention by which one or more people bind themselves, with another or others, to give, do, or not do something.

The German Civil Code prescribes that "for the formation of a binding transaction by legal acts, as for any modification of the content of a binding transaction, a contract concluded between the parties is required, unless the law provides otherwise." For its part, the Swiss Civil Code states that "there is a contract if the parties manifest their reciprocal will in a concordant manner; this manifestation may be express or tacit."

The Civil Code of the former Soviet Union only stated that "legal acts, that is, acts that tend to establish, modify or extinguish civil law relations, may be unilateral or bilateral (contracts)."

The Spanish Civil Code, in its art. 1254, like all those in continental Europe, also follows the trail marked by the Corpus Iuris Civilis of Justinian, as it could not be otherwise according to the sources of Castilian or Aragonese law, adhering to its own tradition; However, the codification work throughout the century in Spain adjusted, among other compilations, to the systematics of the Napoleonic Code. By direct influence of the Digest, the rule is expressed as follows: "the contract exists when one or more people agree to bind themselves, with respect to another or others, to give something or provide some service."[6]​

The Argentine Civil Code, in its art. 1137, establishes that "there is a contract when several people agree on a declaration of common will, intended to regulate their rights."[7]​.

According to the Civil Code of Uruguay (art. 1247), "Contract is an agreement by which one party is obligated to the other or both parties are reciprocally obligated to provide any service, that is, to give, do or not do something."

Influenced by the evolution of civil law in South America, in the Republic of Ecuador in a similar sense it prescribes as a contract in art. 1454 "Contract or convention is an act by which one party is obliged to another to give, do or not do something. Each can be one or many people."

The Civil Code of Bolivia (art. 450) indicates, “There is a contract when two or more people agree to establish, modify or extinguish a legal relationship between themselves.”

In El Salvador, its Civil Code (art. 1309) defines it as “Contract is an agreement by virtue of which one or more people are obligated towards another or others, or reciprocally, to give, do or not do something.”

Contenido

De entre los antecedentes remotos, sobre los que hay mayor grado de coincidencia en la doctrina, pueden citarse los siguientes:.

Roman contractual system

In Roman Law the contract appears as a form of agreement (conventio). The convention is the consent of two or more people who agree on something that they must give or lend. Consensuality was the dominant prototype.

The convention is divided into a pact (pactum) and a contract (contractus), the pact being that which has no name or cause and the contract being that which has one. In this context, a name is understood as the word that produces the action (the pact refers only to relationships that only generate an exception). The cause is some present thing from which the obligation is derived. The pact was gradually assimilated to the contract as actions were considered the instrument to demand compliance.

The contract applies to any agreement of wills aimed at creating civilly enforceable obligations and was always protected by an action that gave it full legal effectiveness.

Contracts are divided into true and quasi-contracts. Those that were based on the express consent of the parties were true and those based on the presumptive consent were quasi-contracts.

In turn, true contracts were divided into nominated and innominated. Nominated were those who had a specific and particular name confirmed by law (e.g. sale) and unnominated were those who, even though they had a cause, did not have a name. There were four unnamed contracts: "I give so that you give", "I give so that you do", "I do so that you give" and "I do so that you do". The characteristic of unnamed contracts is that they did not involve counted money.

In Roman Law there were unilateral and bilateral contracts. Unilateral contracts were binding on only one of the parties (for example, mutual contracts) and bilateral contracts were binding on both parties (as in the case of sale).

The action (Actio) was the other essential element of contracts in Roman Law. Actions relating to contracts are actiones in personam in which the plaintiff bases his claim on a contractual or criminal obligation, which could be Direct and Contrary. Examples of them are:

• - "Actio direct": Direct actions were those that the creditor had, against the debtor, from the moment of the conclusion of the contract, such as. the "actio certi" (which pursues a specific object, sum of money or thing); the "actio ex stipulatio" (which the creditor has when the object was neither money nor generic goods but rather involved an action); the “actio locati” (that the landlord has against the tenant); the “actio commodati direct” (to achieve the restitution of the thing loaned); the “actio depositi direct” (to demand from the depositary the return of the deposited thing); the “actio mandati direct” (to hold the agent accountable for the mandate); the “actio pledgeoraticia direct” (for the owner to recover the thing pledged); the “actio negotiorum Gestiónrum Directa” (to demand accountability from the manager of a business).

• - "Actio Contraria": Actions for which compensation is always requested, that is, they arise after the contract has been made, such as the "actio fiduciae" (for the return of the property transferred as collateral); the “actio redhibitoria” (to terminate the contract if hidden defects are found in the thing sold); the "actio quanti minoris" (by which the buyer demands a reduction in the price of the thing because it does not correspond to the real price), the latter also called "actio estimatoria"; the "actio conducti" (to enforce the lessor's obligations); the "actio commodati contrara" (to obtain compensation for possible damages or expenses caused by the thing given in bailment that has been caused to the bailor; the "actio depositi contrari" (for the depositor to pay the costs of the deposit); the "actio mandati contra" (to demand that the principal accounts for the expenses incurred during the mandate); the "actio pledgeaticia contrasta" (for the pledgee to demand recovery of the damages and expenses caused by the pledged thing); the “actio aerviana” (which allowed the pledger to remain in possession of the invecta et illata that were to serve as collateral); "actio depensi" (for the guarantor to collect from the principal debtor what had not been reimbursed); the "actio poenae persecutoria" (for the reparation of damage); "actio civilis incerti" or "civilis in factum", typical of unnamed contracts; and "actio doli" (criminal action taken against someone who damages with intent).

Some types of contracts in Roman law were:

• - Aestimatum. Contract under which a party receives appraised objects with the obligation to sell or return them after a certain time.

• - Chirographum. Way of being obligated by pilgrims, by virtue of which the debtor gave the creditor a receipt.

• - Syngraphae. Literal way for pilgrims to bind themselves, consisting of two copies, one in the power of the creditor and the other in the power of the debtor.

• - Conventio in manum: Contract verbis by virtue of which when a woman marries, she enters her husband's family, legally occupying the place of a daughter.

• - Depositum: Deposit. Contract that is perfected "Perfection (Law)") with the delivery of the thing that the depositary must return when the depositor requires it.

• - Depositum irregulare: Deposit of money or fungible goods.

• - Dictio dotis. Verbis contract in which the father, a third party or the woman undertake to constitute a dowry.

• - Iusiurandum liberti: Contract verbis by virtue of which the slave undertakes to provide certain services to the master. Also called promissio iurata liberti.

• - Locatio conductio: Lease. One of the parties (locator) undertakes to procure for the other (conductor) the temporary use and enjoyment of a thing or the provision of a certain service (locatio conductio operanum) or the execution of a work (locatio conductio operis), in exchange for an amount of money called merces.

• - Mandatum: Mandate. Contract by virtue of which one person (principal) entrusts another (agent) with the free performance of a certain act, for the account or interest of that person or third party.

• - Pignus: Garment. The debtor, or a third party, delivers possession of a thing to the creditor, as collateral for a debt.

• - Precarium: Unnamed contract by which one of the parties grants the loan of something to the other party, who has specifically requested it (preces) and who is obliged to return it upon the first request.

• - Societas: Society. Contract between two or more people, in order to participate in profits and losses.

• - Stipulatio: Verbal, solemn, unilateral contract stipulation that consists of a question followed by a consistent answer.

• - Transactio: Unnamed contract that consists of an extrajudicial agreement by virtue of which the parties make concessions to avoid the results of the subsequent trial.

Contracts typified in the Seven Items

The Code of the Siete Partidas of King Alfonso The Fifth Part, composed of 15 titles and 374 laws, refers to the acts and contracts that human beings can carry out or celebrate in the course of their life (private law). It deals with the mutual contract, prohibiting the collection of interest or "usury"; of bailment; deposit "Deposit (contract)"); of donation; of sale, with the distinction between title and mode of acquisition (from Roman law); exchange; rental or leasing; of company or partnership; of stipulation or promise; and the bail and the peños (mortgages and pledges "Pledge (rem)")).

It also refers to the payment and transfer of assets. Likewise, it includes important rules of commercial law, referring to merchants and commercial contracts.

Interpretar un texto consiste en atribuir significado preciso a sus palabras. La interpretación de cualquier texto es fundamental, y especialmente lo es en materia de contratos, porque de ella depende la posterior calificación jurídica y determinación de los efectos que el ordenamiento asigna a la manifestación de la voluntad comprendida en sus términos. Tratándose de los contratos su interpretación tendrá en esencia que definir la causa, el objeto y las manifestaciones de voluntad con integración de aquello que, no siendo esencial, falte a su perfección (principio de integración del contrato). El problema de la incoherencia del contrato, en caso de discordia entre las partes, se traslada al juez, que aplicará las reglas interpretativas conforme al principio de legalidad.[8]​.

Interpretation methods

There are several methods of interpretation that may vary depending on the civil code that governs.

But basically two currents are observed, two methods of interpretation: the one that proposes to analyze the text (literally) and the one that proposes to find the common intention of the parties, that is, what the authors wanted to say. Several authors understand that getting to know the common will of the parties is very complex and increases the discretion of the judge.

According to this theory, the judge must seek the solution based on the intentions that the parties had at the time of contracting. The judge's job would then consist of investigating these intentions. It is the option followed, among others, by the Chilean Civil Code (art. 1560) and the Spanish one (arts. 1281 and 1286).

The judge must evaluate the objective data that emanate from the agreement to specify what the common intention of the parties was. It is the option followed, for example, by the French Civil Code and that of Mexico City.[9]​.

Guidelines for the interpretation of ambiguous expressions

Clauses susceptible to two meanings, in one meaning the validity and in the other the nullity of the act, must be understood in the first one.

Equivocal or ambiguous clauses must be interpreted through the clear and precise terms used elsewhere in the same writing.

The facts of the contracting parties, subsequent to the contract, that are related to what is discussed, will serve to explain the intention of the parties at the time of entering into the contract.

Ambiguous clauses are interpreted by what is customary and customary in the place of contract.

Interpretation in favor of the debtor

Ambiguous clauses must be interpreted in favor of the debtor (favor debitoris). But ambiguous or obscure clauses that have been extended or dictated by one of the parties, whether creditor or debtor, will be interpreted against it, provided that the ambiguity comes from its lack of explanation. The above reflects an ancient Roman rule (interpretatio contra stipulator), its foundation is found in the principle of responsibility, which imposes the burden of speaking clearly. Thus the obscurity of the pact must harm the declarant. The generality of consumer protection laws establish that when in doubt it must be interpreted in favor of the consumer.

Theory of unpredictability

The theory of unpredictability also applies to contracts, in the event that, due to radical changes in general economic conditions, the satisfaction of the contract becomes excessively burdensome, and the conditions of the contract must be adjusted so that they resemble what the parties originally had in mind.

Se trata aquí de analizar aquellos actos, causas, hechos, requisitos y formas que, instantánea o sucesivamente, han de confluir para la perfección y cumplimiento del contrato.

agreement of wills

The contract requires the unequivocal manifestation of the will of the parties that will form the legal act. Thus, when the contracting parties express their will at the time the contract is formed, it is called between presents. When the manifestation of will occurs at different times, it is called between absentees. The distinction is important to be able to determine exactly the moment in which the contract enters the legal life of the contracting parties. The contract between those present will come into force at the time of the simultaneous expression of the will, while the contract between those absent only until the last contracting party has given his expression.

Offer and acceptance

• - The offer is a unilateral manifestation of will, directed to another. The classic example is that of a retailer that offers its products to anyone, at a certain price. The offer is mandatory, that is, once issued, the proposer cannot modify it at the time of acceptance by the interested party.

• - The acceptance of the offer must be explicit, so that the other contracting party must show its express or tacit consent, in a way that indicates its unequivocal intention to accept the offer and adhere to the offeror's conditions.

The mandatory validity of the offer varies in different legal systems. For some, the offeror can vary the offer as long as it has not been accepted; However, in others the offer must remain intact for the entire period that, usually or legally, the contracting party is recognized to accept it.

Acceptance in the contract between absent/distant persons

There are various theories regarding the moment in which a contract develops its legal effects when it involves parties that are physically distanced from each other. Various theories come together:

• - Issue theory: It understands that the offer is accepted at the moment the acceptor accepts it.

• - Remission (or issuance) theory: Acceptance occurs at the moment it is accepted and remission of said acceptance is given to the offeror.

• - Reception theory: Acceptance would occur in this case after acceptance, referral and arrival of the latter to the area where the offeror carries out its activity (company, home, etc.).

• - Theory of knowledge: Requires acceptance, referral, arrival in the field and, in addition, knowledge of it. Spanish doctrine leans towards the theory of reception, despite the fact that the theory of knowledge is stricter (see jurisprudence on the matter, or the Automatic Contracting Law).

Pre-contractual stage

The purpose of the pre-contract is the preparation of a future contract. Three different types of pre-contract can be identified:

• - The contrahendo pact. People bind each other to carry out negotiations that result in a future contract. They cannot arbitrarily break off negotiations without incurring contractual liability.

• - The accepted unilateral promise. A subject presents an offer for a future contract to another subject, who agrees to study it and decide whether to accept or reject it. The offeror agrees not to withdraw the offer during a certain period. Only the offeror is bound by this agreement. Commercial proposals are a typical example of this type of pre-contract, where the offering company agrees to keep the offer intact for a certain period, for example, 30 days.

• - The bilateral or reciprocal promise.

El contrato tiene todos los elementos y requisitos propios de un acto jurídico que son los elementos personales, elementos reales y elementos formales.

Essential elements

There are basically three requirements that, in almost all legal systems, the laws require to achieve the effectiveness of the contract: consent, object and cause.

It is the volitional element, the internal will, the will that, manifested under consent, produces legal effects. The perfection of the contract requires that consent be freely given by all the parties involved, due to or effect of the principle of relativity of contracts. The will is expressed by the successive concurrence of the offer and acceptance"), in relation to the thing and the cause that must constitute the contract. Vitiated consent will be void, for having been given by mistake, with violence or intimidation, or fraud, or by a subject other than the object of the contract.

The absence of defects in the consent is essential for the validity and effectiveness of the contract, to which end it is required that the will not be pressured by external factors that modify the true intention. The most prominent vices of consent are: (a) error, (b) violence and (c) fraud.

• - (a) The error: When the error refers, there is a mistake about the object of the contract, or about some of its essential aspects. The error is a reason for nullity of the contract when it falls on the nature of the contract (he wanted to make a lease and made a sale), on the identity of the object, or on the specific qualities of the thing.

The error must not be in bad faith, because otherwise, it becomes fraud.

• - (b) Force or violence: In violence, an irresistible force is exerted that causes serious fear to one of the parties to the contract, or that one of the parties has abused the weakness of the other. The threat of going before a judicial authority to claim a right is not coercion, unless this right is abusively threatened.

• - (c) Fraud: Any artificial, fraudulent or contrary to good faith means, used with the purpose of deceiving, or confusing, to induce a person to consent to a contract that, if they had known the truth, they would not have accepted it, is considered fraud. The victim of fraud can maintain the contract and claim damages.

All things "Thing (Right)") that are not outside the commerce of men, even future things, can be the object of contracts. All services "Service (economy)") that are not contrary to laws, morality, good customs or public order may also be the subject of a contract.

Normally, the civil regulations of legal systems require that there be a just cause for the birth of legal acts. The cause is the determining reason that led the parties to enter into the contract.

A contract has no cause when the manifestations of will do not correspond to the social function that it must fulfill, nor when a cause is simulated or feigned. The contract must have a cause and this must be existing, true and lawful.

• - Source cause: it is the origin or legal fact that generates obligations or a legal act.

• - Purpose: it is the purpose or purpose pursued by the parties when carrying out the legal act or business.

The problem of cause revolves around the 'final cause'. There have been disagreements and debates that still remain active about whether the final cause should be considered an essential element of legal acts. Apparently due to the wording of Art. 944 of the CC it should be. For those who consider that the final cause should not be part of the essential elements of the legal act, they express that it is confused with its object or with its consent. This position affirms that the essential elements of business are: subject, object and form. But for those who consider that the final cause is part of the legal business, they distinguish:

• - The object: as the matter on which the legal act deals, that is, the facts, the things (marketable things, services to be provided, current or future: with what is going to be done) and;.

• - The cause: as the purpose taken into account or in view by the parties when entering into the transaction (origin or legal fact generating obligations: what they want to do and who will be obliged).

• - Difficulty of the subject.

• - Appearance of the problem of cause in the field of law.

Jean Domat was the first to develop the causalist theory of obligations; he maintained that the cause of obligations resided in the consideration exercised by one person in relation to another. His doctrine was followed and disseminated by his disciple Robert-Joseph Pothier, and was later included in the French Civil Code of 1804. These causalists distinguished synallagmatic contracts from real, unilateral contracts and those with free titles. Domat and Pothier required as an element for the validity of a contract "a lawful cause in the obligation."

When the French doctrine of causalism was at its peak"), in 1826 an essay by the Belgian A.-N.-J. Ernst appears, entitled "The cause is an essential element of the contractual obligation." different elements and require four conditions: will, capacity, object and cause, when in reality there are only three. If in gratuitous contracts the cause resides in the freedom of the benefactor, it is also not true that this is in itself an external condition of the existence of such contracts. A feeling that animates the donor cannot be separated from the will that she expresses, to make it an element of the contract.

Planiol affirms that: "The cause is false and useless." It is false because if it is said that in bilateral contracts the cause of the obligation of one of the parties is the performance of the other, it forgets that the performance and the obligation arise at the same time and it is not possible for one thing to be the cause of the other. Most French and European causalists have turned to these theories.

At the end of the century and the beginning of the century, neocausalists have appeared. Indeed, Henri Capitant"), Jacques Maury") and Louis Josserand have revived the theories of Domat and Pothier. The neocausalists were objectivists, they maintained that the cause element is essentially a psychological factor, they conceive the cause as the concrete end, the purpose, the interest that induces the parties to contract, the immediate and determining end that they have had in mind. There is no will without an interest. Modern codes have eliminated the cause in their legislation, others have incorporated it, but there is a marked interest in eliminating it from current codes.

In general terms we can affirm that the Argentine Civil Code alludes to the cause, in its art. 417, when it provides that: The obligations derive from any of the sources established by law. As can be seen, this article incorporates a causalist notion of obligations. Now, when we talk about the cause in the new code, it can be said that practically nothing has changed in relation to its predecessor, we are referring to the Vélez Sarfield code.

Personal items

The subjects of the contract may be natural persons (individuals) or legal entities, with the capacity to act legally, necessary to be bound. In this sense, capacity in law is subdivided into capacity to enjoy (the legal capacity to be the holder of subjective rights, commonly also known as legal capacity) and capacity to exercise or act, active or passive (legal capacity to exercise rights and contract obligations without assistance or representation from third parties, also known as capacity to act).

real elements

They integrate the so-called performance and consideration, that is, the thing or service that is the object of the contract, on the one hand, and the delivery of a sum of money in exchange for it, or another agreement, on the other.

Formal elements

The form is the set of signs by which the consent of the parties is expressed in the conclusion of a contract. Some contracts may require a specific form of conclusion. For example, the written form may be necessary, the signature before a notary or before a notary and before witnesses, etc. In the case of written form, the document may include the following sections: background or recitals, declarations and clauses.

Accidental elements

They are those that the parties establish through special clauses, which are not contrary to the law, morality, good customs, or public order. For example: the term, the condition "Condition (Law)"), the mode "Mode (law)"), solidarity, indivisibility, representation, etc.

In accordance with the autonomy of the will, the contracting parties can establish the agreements, clauses and conditions that they deem appropriate, as long as they are not contrary to the law, morality, good practices and customs, or public order.

The form can be decisive, sometimes, of the validity and effectiveness of the contracts. Contracts can be verbal or written; verbal, if its content is preserved only in the memory of the participants, or written, if its content has been transformed into grammatical text reflected or recorded on a permanent and durable medium (paper, visual or sound magnetic tape, CD, DVD, PD, etc.) that allows its reading and exact subsequent reproduction.

Contracts that are in electronic or digital form (those that are not signed on paper) have the same validity as any other contract as indicated in the UNCITRAL Model Law on electronic commerce in its articles 5 and 11.[11]​.

Written contracts can also be solemn or not, depending on whether they must be formalized in a notarized public deed, and even if the law requires their registration in some type of public registry (Property Registry, Commercial Registry, Registry of cooperatives, Registry of collaborating urban planning entities, etc.). In so-called real contracts, the perfection of their form also requires the delivery of the thing (for example, the loan, even if it is recorded in a public deed, does not arise if the capital "Capital (finance)" lent is not delivered in the act of signing the contract).

In some States of the European Union there is regulation on the font size of contracts with consumers (e.g. Spain, France, Portugal).

The font size of the contracts is a validity requirement that is included in the accessibility and legibility of the general contracting conditions with consumers. In Spain it is regulated in article 80.1.b) of the Consolidated Text of the General Law of Consumers and Users.[12] If the letter does not have the established minimum legal size, the contract or the general condition without the legal size is null or there is no so-called "incorporation" of the general condition.

The font size of contracts is usually regulated in typographical point and/or in millimeters. To understand the equivalence, the convention is that a 1 Typographic Point is equivalent to 0.3527mm*.* In Spain the font size of the contract may not be less than 2.5 millimeters (equivalent to a size 7 in Typographic Point,[13]​ according to the equivalence 1 Typographic Point = 0.3527mm) from June 1, 2022; Until that date arrives, the minimum font size is 1.5 millimeters.

Citamos, a continuación, las clases más comunes, sobre las cuales la doctrina es coincidente, y que son:.

Unilateral and bilateral contracts

• - Unilateral contract: it is an agreement of wills that generates obligations only for one party.

• - Bilateral contract: it is the agreement of wills that gives rise to obligations for both parties.

• - Multi-party contract: it is the agreement of wills that gives rise to contracts between two or more parties (e.g.: in the Civil Code of Colombia, Art. 507. Definition of Participation Accounts. Participation is a contract by which two or more people... ommisis.), for which it is assumed to be multi-parties.

• - When in a unilateral contract there are obligations that imply the transfer of something, if it is destroyed by chance or force majeure it is necessary to be able to establish who should suffer the loss. The thing always perishes for the creditor (in transfer contracts of ownership the creditor is the owner; while in transfer contracts of use, the creditor for restitution is the owner and the thing perishes for him). If the contract were bilateral, there would be no possibility of raising the problem, because this issue assumes that since the obligations are reciprocal, one party does not comply by delivering the thing, due to a case of force majeure and in view of this the other party must comply, since the debtor's non-compliance is not attributable.

• - The exception of unfulfilled contract (exceptio non adimpleti). In all bilateral contracts, which generate reciprocal obligations, when one party does not comply or agrees to comply, it lacks the right to demand that the other comply with its obligation, and if despite this it intends to judicially demand compliance by means of a lawsuit, the defendant will raise the exception of unfulfilled contract (principle "default (right) purges default"). The exceptio non adimpleti cannot be presented in unilateral contracts, for the simple reason that in them only one of the parties is obliged, and if it does not comply, the other may judicially demand compliance, without said exception being able to be opposed to it, since it has no obligation to perform on its part.

Onerous and free contracts

• - Onerous contract: it is one in which there are reciprocal benefits and encumbrances, in this there is an equivalent sacrifice made by the parties (equivalence in reciprocal benefits); for example, the sale, because the seller receives the benefit of the price and at the same time delivers the thing, and vice versa, the buyer receives the benefit of receiving the thing and the burden of paying.

• - Free contract: its purpose is only the utility of one of the two parties, with the other suffering the burden. Therefore, a contract in which the benefit is for only one of the parties is free, such as a bailment.

Commutative and random contracts

This classification only applies to bilateral contracts.

• - Commutative contract: is that contract in which the performances that the parties owe are certain from the moment the legal act is concluded, a very clear example is the contract for the sale of a house.

• - Random contracts: is one that arises when the benefit depends on a future and uncertain event and at the time of contracting, the profits or losses are not known until the moment this future event occurs. Examples are the harvest sale contract called "hope", betting, games, etc.

Among the common characteristics of random contracts are:

• - Uncertainty about the existence of an event, as in a bet, or about the time of realization of that event (when).

• - The opposition and not only the interdependence of benefits, because when uncertainty ceases, one of the parties necessarily wins and the other loses, and, furthermore, the measure of the gain of one of the parties is the measure of the loss of the other.

It is important to note that the Dictionary of the Spanish Language defines the term random, from the Latin aleatorius which means, typical of the game of dice, adj. Of or relating to the game of chance.

Main and accessory contracts

• - Main contract: is one that exists by itself, while the accessories are those that depend on a main contract. The accessories follow the fate of the main thing because the nullity or non-existence of the first ones, in turn, causes the nullity or non-existence of the accessory contract.

• - Accessory contracts: they are also called "guarantee contracts", because they are generally established to guarantee the fulfillment of an obligation that is considered primary, and this form of guarantee can be personal, such as bail, in which a person undertakes to pay for the debtor, if he does not do so; or real, such as the mortgage, the pledge "Pledge (real right)"), in which a real right is constituted over an alienable asset, to guarantee the fulfillment of an obligation and its preference in payment.

The rule that the accessory follows the fate of the main thing suffers in certain cases from exceptions, because the accessory contract could not exist without the principal contract being previously established; However, the Law presents us with cases where there may be a bond, pledge or mortgage, without there yet being a main obligation, as occurs when future or conditional obligations are guaranteed.

Instant and subsequent contracts

• - Instant contracts, or single contract, are those that are fulfilled at the same time they are celebrated, that is, their fulfillment is carried out in a single act.

• - Successive Contract Contract: is one in which the performance of the benefits is carried out in a specific period, and which, at the request of the parties, can be extended to satisfy their primary needs and these terms can be:

• (a)Continuous execution: single execution but without interruption.

• (b) Periodic execution: various services that are executed on established dates.

• (c) Intermittent execution: occurs when requested by the other party.

Characteristics of the executions are: The execution is autonomous from the others, so each act is autonomous. There is retroactivity for each legal act that is carried out. If an illegal element is present, what should be done is to cancel any service already provided.

Consensual and real contract

• - Consensual contract: as a general rule, the consent of the parties is sufficient to form the contract; Obligations arise as soon as the parties have agreed. The consent of the parties can be expressed in any way. However, it is necessary that the will to contract have a particular form, which allows its existence to be known through it. It is not the simple coexistence of two internal wills that constitutes the contract; It is necessary that these be manifested outside.

• - Real contract: it is concluded from the moment in which one of the parties has made to the other the tradition or delivery of the thing about which the contract relates.

Formal, solemn or non-solemn, and non-formal contract

• - Formal contract: is one in which the law orders that consent be expressed by a certain means for the contract to be valid. In the legislation, an eclectic or mixed system is accepted with respect to formalities, because in principle, the contract is considered to be consensual, and only when the legislator imposes a certain formality must it be complied with, because otherwise the act will be affected by nullity. For example, the purchase and sale of real estate that must be granted by public deed.

• - Solemn formal contract: is one that, in addition to the manifestation of consent by a specific means, requires certain rites stipulated by law to produce its own effects. Vg. Marriage and divorce

• The formalities will be ad probationem when they must be carried out in order to demonstrate the celebration of an act; It generally consists of carrying out the act before a notary or public official for this purpose.

• The formalities will be ad solemnitatem when the will of the parties, due to legal requirements, requires a particular formality without which the contract has no legal effectiveness.

The distinction between formal and solemn contracts lies in what refers to the sanction. The lack of form causes relative nullity, or failing that, unenforceability before third parties; the lack of solemnity causes nonexistence.

Private and public contract

This classification meets various criteria:

(1) According to advertising or professional intervention in the contract:.

• - Private contract: is the one made by the people involved in a contract with or without professional advice. It will have the same value as the public deed between the people who sign them and their successors.

• - Public contract: these are contracts authorized by public officials or employees, always within the scope of their powers, and have better evidentiary status. Notarial documents are those that have the greatest importance and within them mainly public deeds.

(2) According to the quality of the participating subjects:.

• - Private contract: is the one made between natural or legal persons, whether public or private, in which there is relative contractual equality, with no powers that one can impose on the other.

• - Public or administrative contract: is the one concluded between the State or a public body and a natural or legal person, where the first of them maintains a series of powers over the second, called exorbitant, which place the latter in subordination to the former.

(3) For its advertising:.

• - Public: when they are carried out under the authority of notaries or judges.

• - Private: are contracts granted by the contracting parties without the authorization or existence of a notary public, although they may have the presence of witnesses.

Nominated or typical and innominated or atypical contract

• - Nominated or typical contract: is that contract that is provided for and regulated by law. Therefore, in the absence of agreement between the parties, there are dispositive rules to which to resort. (Purchase, leases...).

• - Unnamed contract or atypical: it is one for which the law does not have a specific name, because its characteristics are not regulated by it. It can be a hybrid between several contracts or even a completely new one. To fill in gaps in the law or situations not foreseen by the parties in the contract, it is necessary to resort to the regulation of similar or analogous contracts.

It is important to mention that unnamed contracts are not those that are not provided for by the civil code, because all contracts are; They are simply those that are not expressly defined in its articles, although, without prejudice to the parties expressly defining them at the time of contracting, within the framework of their autonomy of will.

Contracts determined solely in their kind

They are those in which only mention is made of the quantity and quality of the object of the contract, for example: The sale of 100 metric tons of soybeans. As you can see, it is not indicating which soybeans are sold; In this case it must be assumed that the quality is average.

The number of contract types that a legal system that has freedom of contract can offer is unlimited, as are the rights and obligations that the parties can create are almost infinite, including doing so in a pure and simple manner, or subject to some modality. However, the civil legislation of most countries has regulated the most important of these, either in their respective civil codes, or in special laws, creating a system of typical contracts or nominated, whose essential regulation appears in the laws and is removed from the parties of the contract, for the purposes of security, protection and balance between the possible subjects. The "typicality of contracts" is made effective through the "principle of contract integration", applied either in accordance with the formulation that the parties have attributed to their contract, or as deduced from the content of the clauses of the text, if the terms in which the contract has been formulated by the parties are unclear.

Effects between the parties

"The contract is law between the parties" is a common expression (contractus lex). However, this does not mean that contracts have power equivalent to that of laws. The fundamental precepts arising from the contracts, which the parties involved must observe, will be the following:

The parties must comply with the conditions stipulated in the contract (principle of literality).

The conditions and effects of the contract only have effect between the parties who accepted the contract, and their successors in title (principle of relativity of the contract).

The agreements contained in the contracts must be executed in the terms that were signed.

The stipulations of typical contracts, which are contrary to the law, are considered not in place.

Legal provisions recognize the contract as a source of obligations. Contractual obligations are civil obligations, so the creditor can demand from the debtor the satisfaction of the debt as agreed. In the event that compliance with the object of the obligation is not possible, by equivalence, the creditor may demand compensation for damages. Once a contract has been validly created, it becomes inalienable, and the obligations originated by the valid contract cannot be modified unilaterally.

Effects on third parties

In principle, contracts only have effects between the parties that form it. However, there are contracts that do have effects on third parties "Third Party (right)"). A third party is a subject who did not participate in the formation of the contractual relationship, and who, therefore, did not express his/her will regarding the contract. It may even be that the third party did not even know of the existence of the agreement.

(a) Effects regarding successors.- The affirmation that contracts bind heirs will fundamentally depend on the notion of succession that is handled in the legal system in which the opinion is issued. Thus, in legal systems such as the Costa Rican and Peruvian, confusion of assets does not operate, that is, the hereditary assets are responsible for the obligations of the deceased and not the assets of the heirs. On the other hand, in legal systems such as the Italian one, confusion of assets occurs, so the heirs respond even with their own assets for the obligations of their deceased (unless they accept with the benefit of inventory, if such an option exists).[14]​.

The nullity of the deceased's contracts after the succession affects the successors, as they may find themselves in the situation of having to return to third parties "Third Party (right)"). Additionally, individual successors in title will be affected by the restrictions imposed by the deceased, for example, a mortgage, an easement or a usufruct right in favor of another.

(b) Effects regarding unsecured creditors.- Any contract of the debtor that affects his assets implies a consequence for the guarantee of the unsecured creditor. To protect it, oblique action and Paulian action have been established, however, each of them can only be invoked under certain conditions. Namely, the oblique action can only be exercised by the creditor due to the debtor's inaction in protecting his own assets, and the Paulian action can only be exercised against a debtor who is in a state of insolvency.

(c) Effects regarding penitus extranei.- The penitus extranei are all those people outside a contractual relationship. Even so, the effects of the contracts are enforceable against these third parties, since they cannot claim ignorance of the legal act and its effects, as would be the case of real or personal rights registered in a public registry with legal effectiveness, marriage agreements, and the registrations of civil or commercial companies.

In principle, obligations cannot be assigned to subjects who have not participated and consented to the formation of the legal bond. But the case of the constitution of benefits in the name of third parties "Third Party (right)") is different.

Used as a method to obtain legal security, in a generic sense, the guarantee is one of the consequences of contracts, especially onerous transfers, insofar as its existence attributes to the parties the unquestionable power to acquire, occupy, demand or maintain the transferred real or personal right, wieldable both against the person who has transferred it, and against third parties, who must therefore cease pursuing the same object of the contract, so that, by its virtue, the subject can persist in enjoyment. peaceful benefit, or equity, obtained through the contract.

The most obvious "Proof (right)") of the contract protection system is found in the "remediation by eviction" and the "remediation due to hidden defects" to which the transferors are legally subject in a contract, a point of protection is created with which it is provided that in the event that the acquirer is stripped of the object due to a vindictive action by a subject with a better legal title (reipersecutoridad), the "guarantee for eviction" and the transferor must return not only the value of the thing, but also the legal expenses of the contract and the action taken to the contrary, if applicable. The same happens with the "hidden vices" of the transmitted good. So, one thing is the “guarantee of contracts” and another is the “guarantee contracts”. The latter in themselves contain the two virtues, that is, they are a generic guarantee of their content for the subjects who have signed them and they also contain, as part of their object, the merit of ensuring compliance with another contract or different obligation. Examples of the latter are guarantee contracts, comfort letter, stand-by letter, bond, pledge "Pledge (rem)"), mortgage, antichresis, insurance, etc.

Los principales elementos que concurren en un contrato de título oneroso son.

1. • La consolidación de la deuda. El contrato en sí mismo.

2. • La consolidación del instrumento de pago o de su efectivo ejercicio. Los elementos ejecutivos tangibles que dan a su valor residual exigible.

Caso contrario, se establece la duda razonable acerca del cumplimento efectivo del contrato, donde el acreedor es quien posee la carga de la prueba.

En la acción práctica del pago del deudor, es una función exclusiva y obligada por el acreedor dar fe de que el pago se ha realizado o se encuentra al corriente de pago, pero este jamás puede constituirse en juez y parte iudex et iudices ya que resulta ab absurdo esta posición, porque nunca puede decidir de manera imparcial como consecuencia de su propio interés. No puede ser el mismo acreedor quien determine la posición del deudor, situación que define un testis unus, testis nullus [testimonio único, testimonio nulo].

A título de ejemplo es el caso de cuando una entidad siendo parte del contrato a su vez resulta Juez en la determinación del pago.

Perfect debt consolidation and payment

There are two formulas to prevent the creditor from being judge and party, not committing a taint of partiality, and at the same time being able to demonstrate the existence of their creditor position of a total or partial debt in the signed contract.

1. • The imperative mediation of a third party, who receives the debtor's payments, to make them effective for the creditor. Therefore, this third party is the true witness who unequivocally gives independent and effective testimony to the parties of the state of partial or total compliance with the contract.

2. • The issuance of the respective documents (bills, promissory notes, etc.) that certify the payment as well as the capacity for collection by the creditor, when these are in their possession.

Any of these two elements are sufficient for the creditor to attest to the fulfillment of the debtor's obligations since the first interposes an independent witness and the second genuine instruments that in the debtor's possession legitimize and reliably accredit the amount owed.

From the legitimate intermediary

The intermediary who acts in a completely impartial manner by becoming a valid witness eliminates the presumption of testis unus, testis nullus, thus perfecting and certifying the creditor's argumentative validity in its entire scope.

From the collection instrument

In the absence of an impartial intermediary to accredit the operation, only the collection instrument survives as an element that perfects the enforcement procedure of the debt that the creditor wants to enforce.

In this way, all doubt about the debt is diluted and the creditor has all independent evidence without falling into the figure of "judge and party" which makes it impossible for him to be able to make the claim for a debt effective, since any settlement unilaterally prepared on his part, which does not have any legal force since the collection instrument becomes possessory constitution of the debt in question, because this obligation is accessory sequitur principale to the debt, among which There are collection instruments, unique for the effective accounting materialization of the payment ad probationem, which also establishes the existence of the remainder owed.

It is evident that the debtor has the power to alienate or simply destroy the proof(s) of these obligations so that they are not appropriated by third parties or due to the risk of falling into the hands of the creditor and the creditor is entitled to exercise the collection of said instrument.

There is no different way for the creditor to make a collection claim, in the absence of said instrumentation.

Uncertain computer qualification - Loss of Right by omission

The development of computing has left gaps in matters of law, imposing the technique as a validator of a Judicial process.

It is an erroneous condition to establish that the computer method is sufficient proof, as if it were an impartial third party intermediary. But it should not be forgotten that it is totally plausible to errors, but much more important is to consider that for the purposes of legal doctrine, it remains unilateral proof, although its processing speed and versatility are impressive.

Unfortunately, this is not the case, it does not perfect collection elements but rather leads to an irregular treatment of the law, when on the contrary, computer processing is precisely the ideal means to facilitate the issuance of collection instruments, simplifying this due to its automatic issuance.

Invalidity of credit execution due to lack of instruments

The legal truth is that the lack of the figure of the impartial intermediary as observer and its certification, as well as the lack of collection instruments, removes validity in natura from the collection certification, with the creditor intending to use only its own information and accounting entries, whether or not it is systematized in a computerized manner or by other means.

Under no circumstances, regardless of manual or technological means, can the creditor be the Judge and party to a process.

On the other hand, when in each payment the creditor delivers the promissory note or bill to the debtor, in this act the obligation of an installment, final payment, partial payment, etc. is extinguished. from the moment there is a contract that supports the obligation and the promissory note or letter that supports the veracity of the payment.

Formal execution

Since there is no impartial intermediary, the issuance of collection instruments is the only valid system, when it is the creditor who intends to execute a debt with a declaration presented in his judgment and value.

The consolidated debt is then simply the algebraic sum of the collection instruments in the creditor's (the creditor's) possession. The lack of existence of the collection documents terminates the obligation, canceling the debt and both parties have one.

Contractual liability is that which arises from the contract (unlike non-contractual liability) and requires that the party (subject) who demands it be linked by a contractual link to the person who owes it. The notion of non-compliance is widely debated in comparative law, however, it can be reduced to three main options.[15] Non-compliance is considered to be the non-verification tout court of the provision in its materiality, the non-achievement of the committed result and the specification of types of contractual infractions.

The choice of each of these options will incline the legal system to prefer a subjective or objective interpretation of liability.

Contracts are elements that are considered of "incomplete nature" given the difficulty of reflecting in them all possible contingencies.[16] In addition to this, contracts that lack any of the essential elements are ineffective, or even if these are present, they are nevertheless flawed in some way. Ineffectiveness has different manifestations and effects depending on the type of invalidity caused to the contract. In this regard, they are a consequence of typical disabling defects:

• - Voidability.

• - Nullity.

• - Resciliation.

• - Termination.

• - resolution.

• - revocation "Revocation (Right)").

• - Contract simulation.

• - Portal:Law. Content related to Law.

• - Quasi-contract.

• - Commercial contract.

• - Vices of the will.

• - Contract simulation.

• - Abusive clause.

• - Baudrit Carrillo, D.: Civil Law IV, Volume I. General Theory of Contract. 3rd edition, 2000.

• - Betancourt Serna, F.: Classical Roman Law. Ed. University of Seville. Publications Service. Seville, 2001 - ISBN 84-472-0614-9.

• - Brenes Córdoba, A.: Treatise on Contracts. 5th edition. 1998.

• - Castán Tobeñas, J.: Spanish civil law, common and regional. T-III. Law of obligations. The obligation and the contract in general. Reus Editorial. Madrid, 1977 - ISBN 84-290-1215-X, pp. 399 to 608.

• - Castán Tobeñas, J.: Spanish civil law, common and regional. T-IV. Law of obligations. The particular obligatory relationships. Reus Editorial. Madrid, 1977 - ISBN 84-290-1177-3.

• - Díez-Picazo and Ponce de León, L., and Gullón Ballesteros, A.: Civil Law System. Volume II.. General contract theory. The mandatory relationship in general. Obligatory relationships in particular. 1st edition. Tecnos Editorial. Madrid, 1977.

• - García Medina, J.: New and special forms of guarantee in commerce. Systematic and critical study. Ed. La Ley. Madrid, 2009 - ISBN 978-84-8126-209-4.

• - Kozolchyk, B.: Commercial contracting in Comparative Law. Ed. Dikynson. Madrid, 2006 - ISBN 84-9772-877-7.

• - Lasarte Álavarez, C.: Law of obligations. Principles of Civil Law II. Ed. Marcial Pons. Madrid, 2006.

• - Pérez Vargas, V.: Private Law. 3rd edition. Ed. Lehmann Bookstore. San José "San José (Costa Rica)"), 1994.

• - Ruiz Prieto, E.: Theory and characteristics of contracts according to the Civil Code[2], Ruiz Prieto Asesores Blog, 2016.

• - Ruiz Vadillo, E.: Civil law. Introduction to the theoretical-practical study. Ed. Ochoa. Logroño, 1987 - ISBN 84-7359-272-7 - pp. 305-361.

• - Stiglitz, Rubén: "Contracts. General Theory" (Director and author of Cátedra's collective work), Depalma, Bs. As., t. I, 1990 and t. II, 1993.

• - Stiglitz, Rubén: "Civil and commercial contracts. General theory", two volumes, Abeledo-Perrot, 1998/1999.

• - Contract | Legal Recourse. Page on conceptual issues of contracts.