• - final inventories: they are carried out every time the fiscal period closes, usually on December 31;

• - periodic inventories: they are carried out every certain time within a company;

• - initial inventories: all the company's assets are recorded; Only assets existing on the day(s) of production are documented. It is generally prepared at the beginning of the accounting period, which is usually January 1;

• - legal and political settlement inventories in their process;

• - inventories of products in the manufacturing process: include goods that a manufacturing or industrial company has acquired and are still in the manufacturing process; are quantified through the amount of materials, labor or manufacturing expenses"), applicable to the closing date");

• - raw materials inventories: include materials that are required for the production of products and that have not yet been processed in any way;

• - factory supply inventories"): include all materials that are used to make the products, but that cannot be exactly quantified; for example, paint, sandpaper, nails, lubricants;

• - production in process inventories;.

• - inventories of finished products: those of products that manufacturing or industrial companies acquire and then modify or transform to sell them as products manufactured by them;

• - inventories of materials and supplies; These are those materials with which the products made in a company are made, but which cannot be quantified in an exact way. In which they can be: Paint, sandpaper, nails, lubricants, etc.

• - specific inventories;

• - forest inventories;

• - management inventories;

• - perpetual inventory: help prepare financial statements for periods of time (monthly, quarterly or provisionally); The business can calculate the cost of ending inventory and the cost of goods sold directly, without taking an inventory;

• - physical inventory;[3]​ The Physical Inventory is a physical statistic or count of the assets existing in an organization to identify it and compare it against the existence recorded in the books. The Physical Inventory process requires a periodic verification of the stocks of Fixed Assets that an organization has in order to verify the degree of effectiveness in the administration and control of its assets. The importance of a Physical Inventory is to gather relevant information that describes in detail the state of the assets in such a way that when making a query the real condition of the asset is reflected, in a way that allows pertinent decisions to be made in the case.

• - mixed inventory;[4]​ Mixed inventory, of a class of merchandise, whose items have not been identified or cannot be identified with a particular lot, among the characteristics we have, inventory of finished products, inventory of raw materials, inventory in transit, inventory in process, inventory on consignment, minimum inventory, maximum inventory, available inventory, online inventory, aggregate inventory, quarantine inventory.

• - inventory in transit;[5]​ counts all the materials and products that are about to arrive from suppliers to the company. That is to say, they are also part of the entity, only they are simply in motion.

• - inventory on consignment;.

• - maximum inventory;.

• - minimum inventory;.

• - available inventory;[5]​ refers to that which is available at that moment for the sale or production of new products. The one that, as its name says, is in perfect readiness to be used whenever it is required.

• - online inventory;.

• - added inventory;.

• - quarantined inventory;[5]​ is the inventory that must maintain a waiting time before it can be used in the production process. Naturally, they have to be products with a long life before they expire.

• - forecast inventory;.

• - merchandise inventory;

• - fluctuation inventory;.

• - anticipation inventory;.

• - intermittent inventory;.

• - seasonal inventory;.

• - permanent inventory;.

• - Cyclical inventory: allows high turnover items to be counted more frequently than obsolete items;

• - zero inventory;.

• - inventory of Cultural Heritage "Cultural Heritage of the Nation (Peru)") Intangible: as it appears in the Convention for the Safeguarding of the Intangible Cultural Heritage of UNESCO") (2003).

• - Surprise inventory: it is an unexpected check of a company's assets, carried out without prior notice. The objective is to ensure that accounting records match physical reality, helping to detect errors or fraud in time.[6]​.

• - Reduce ordering costs. When ordering a batch of raw materials from a supplier, a cost is incurred for processing the order, tracking the order, and receiving the purchase in the warehouse. By producing a larger number of batches, larger inventories will be maintained, but fewer orders will be placed during a given period, thereby reducing annual ordering costs.[7]​.

• - Reduce costs due to missing materials. By not having material available in inventory to continue production or meet customer demand, costs are incurred. Among them, lost sales, dissatisfied customers, costs for delaying or stopping production. In order to have protection to avoid shortages, additional inventory, known as safety inventory, can be maintained.

• - Reduce acquisition costs"). In the purchase of materials, the acquisition of larger lots can increase raw material costs; however, smaller costs can be reduced due to quantity discounts and lower freight and material handling costs. For finished products, larger lot sizes") increase in-process and finished product inventories; However, average unit costs could be lower because machinery and technology costs are distributed over larger lots.

It is desired to reduce inventories because, as levels increase, certain costs increase, for example:

• - Storage cost. Among the costs incurred to store and manage inventories are: interest on debt, unused interest that would be earned on income, warehouse rent, conditioning, heating, lighting, cleaning, maintenance, protection, freight, receiving, materials handling, taxes, insurance and administration.

• - Difficulty responding to customers. The existence of large inventories in process clogs production systems, increases the time necessary to produce and deliver orders to customers, which decreases the ability to respond to changes in customer orders.

• - Cost of coordinating production. Large inventories clog the production process, requiring more staff to resolve traffic problems, resolve production congestion, and coordinate schedules.

• - Costs due to reduction in capacity. Materials ordered, held, and produced before they are needed waste production capacity.

• - Costs for defective products in large batches. When large batches are produced, large inventories are obtained. When a large batch is defective, large quantities of defective inventory are stored. Smaller batch sizes (and thus a reduction in inventory levels) can reduce the amount of defective materials.

Contenido

Los costos relevantes de los involucrados en la administración del desarrollo de los inventarios") son:.

Order cost

The cost generated by the activities carried out in a stock replenishment request is called "order cost", which may include, for example, the cost of paper, the cost of the telephone, the preparation cost and others.

Inventory storage cost

"Storage cost" is called "all the processes and activities carried out to maintain the order, good condition and existence of the inventory within the plant, including the cost of fixed assets of the product"), the cost of cleaning"), the cost of space").

Total inventory cost

The total inventory cost is the sum of the two previous costs: annual storage cost and annual ordering cost, according to the following formula:.

CT = total annual inventory cost.

Q= order size to replenish inventory, in units.

C= value of item handled in inventory, in $$/unit.

h= handling cost as a percentage of the item's value, percentage/year.

D= annual demand for items, which occurs at a certain constant rate over time, in units/year.

o= acquisition cost, in dollars/order.

When and how much are the questions on which stock management is based. In effect, if the inventory is replenished in short periods of time, the quantity ordered must be small, which reduces the cost of storage" but increases the cost of placing orders; if the inventory is replenished in long periods of time, the quantity ordered must be large, which reduces the cost of placing the order, but increases the cost of storage").

In inventory management there are inventory replenishment models that try to balance costs and reduce them as much as possible. With these models it is possible to know how much to order and when to order.

With fixed order interval models, an optimal fixed interval is determined for carrying out inventory reviews. Then each time an order is placed, stock is requested for the difference between some maximum and the quantity on hand.

POQ") determines the number of demand periods that will be covered by each order. This interval is calculated using the average demand and rounded to the next integer greater than zero. Each ordered quantity covers the projected requirements for the next interval with orders varying according to the requirements.

This algorithm is a heuristic approach to determining lot sizes that determines them by balancing ordering and storage costs. Selects the number of periods that should be covered by a replenishment order such that the accumulated storage costs barely exceed the ordering costs. Due to the discrete nature of requirements, an order size increases to the same extent that cumulative storage costs are less than or equal to the order cost. The goal is to determine lot sizes that include an integer number of periods.

This algorithm is similar to the PPA algorithm, except that instead of balancing cumulative storage and ordering costs, it balances incremental costs. The algorithm increases order sizes as incremental storage costs are less than or equal to order costs. The objective is to determine lot sizes that include an integer number of requirement periods. Similarly to the previous method.

Los siguientes modelos dan respuesta a la pregunta: ¿Cuánto pedir?

Economic Order Quantity (EOQ)

It consists of finding the point at which the costs of ordering the items and the costs of keeping them in inventory are equal. This is a method that does not give an optimal solution, but it is close to it.

Economic Production Lot (EPQ)

Items are produced and added to inventory gradually rather than in a single order. The EPQ model assumes continuous gradual releases to inventory (finite replacement rate) throughout the production period. With a finite replacement rate, the inventory level will never be the size of the production lot, since production and consumption occur simultaneously during the production period.

Silver and Meal Heuristics

Edward Silver") and Harland Meal") developed the Silver-Meal") heuristic model based on determining the average cost per period as the number of replacement periods increases. A replenishment order is placed when the first average cost increases. This method selects lot sizes that include an integer number of requirement periods such that the total relevant costs (storage and ordering costs) per period are minimized. This method guarantees a local minimum for the current order. Two situations in particular Where this algorithm does not work well are: (1) when the demand rate decreases rapidly over time and (2) when there are a large number of periods with zero demand.

Minimum unit cost

This method is similar to the Silver-Meal algorithm except that, instead of averaging costs across periods, it averages costs across units. This heuristic determines the average cost per unit as the number of periods in a replenishment order increases. An order is shipped when the average cost per unit first increases. The replacement period is reset and the procedure is repeated until lots are obtained in the time horizon.

The ABC" system is used to classify materials according to the economic value they represent in the inventory.

• - Materials A represent 75% of the inventory value. They represent only 20% of materials that must be in inventory.

• - B materials represent 20% of the inventory value and 30% of the materials in inventory.

• - C materials represent 5% of the inventory value and 50% of the materials in inventory.

With this system, it is deduced that it is most convenient for the materials that maintain a greater volume in the inventory to be those that represent the lowest cost.

Exceptions from the ABC system must be made for certain types of materials:.

• - critical materials for production.

• - materials with short storage life.

• - large and bulky materials.

• - bulky materials subject to theft.

• - Stock.

• - Inventory valuation.

• - final inventories: they are carried out every time the fiscal period closes, usually on December 31;

• - periodic inventories: they are carried out every certain time within a company;

• - initial inventories: all the company's assets are recorded; Only assets existing on the day(s) of production are documented. It is generally prepared at the beginning of the accounting period, which is usually January 1;

• - legal and political settlement inventories in their process;

• - inventories of products in the manufacturing process: include goods that a manufacturing or industrial company has acquired and are still in the manufacturing process; are quantified through the amount of materials, labor or manufacturing expenses"), applicable to the closing date");

• - raw materials inventories: include materials that are required for the production of products and that have not yet been processed in any way;

• - factory supply inventories"): include all materials that are used to make the products, but that cannot be exactly quantified; for example, paint, sandpaper, nails, lubricants;

• - production in process inventories;.

• - inventories of finished products: those of products that manufacturing or industrial companies acquire and then modify or transform to sell them as products manufactured by them;

• - inventories of materials and supplies; These are those materials with which the products made in a company are made, but which cannot be quantified in an exact way. In which they can be: Paint, sandpaper, nails, lubricants, etc.

• - specific inventories;

• - forest inventories;

• - management inventories;

• - perpetual inventory: help prepare financial statements for periods of time (monthly, quarterly or provisionally); The business can calculate the cost of ending inventory and the cost of goods sold directly, without taking an inventory;

• - physical inventory;[3]​ The Physical Inventory is a physical statistic or count of the assets existing in an organization to identify it and compare it against the existence recorded in the books. The Physical Inventory process requires a periodic verification of the stocks of Fixed Assets that an organization has in order to verify the degree of effectiveness in the administration and control of its assets. The importance of a Physical Inventory is to gather relevant information that describes in detail the state of the assets in such a way that when making a query the real condition of the asset is reflected, in a way that allows pertinent decisions to be made in the case.

• - mixed inventory;[4]​ Mixed inventory, of a class of merchandise, whose items have not been identified or cannot be identified with a particular lot, among the characteristics we have, inventory of finished products, inventory of raw materials, inventory in transit, inventory in process, inventory on consignment, minimum inventory, maximum inventory, available inventory, online inventory, aggregate inventory, quarantine inventory.

• - inventory in transit;[5]​ counts all the materials and products that are about to arrive from suppliers to the company. That is to say, they are also part of the entity, only they are simply in motion.

• - inventory on consignment;.

• - maximum inventory;.

• - minimum inventory;.

• - available inventory;[5]​ refers to that which is available at that moment for the sale or production of new products. The one that, as its name says, is in perfect readiness to be used whenever it is required.

• - online inventory;.

• - added inventory;.

• - quarantined inventory;[5]​ is the inventory that must maintain a waiting time before it can be used in the production process. Naturally, they have to be products with a long life before they expire.

• - forecast inventory;.

• - merchandise inventory;

• - fluctuation inventory;.

• - anticipation inventory;.

• - intermittent inventory;.

• - seasonal inventory;.

• - permanent inventory;.

• - Cyclical inventory: allows high turnover items to be counted more frequently than obsolete items;

• - zero inventory;.

• - inventory of Cultural Heritage "Cultural Heritage of the Nation (Peru)") Intangible: as it appears in the Convention for the Safeguarding of the Intangible Cultural Heritage of UNESCO") (2003).

• - Surprise inventory: it is an unexpected check of a company's assets, carried out without prior notice. The objective is to ensure that accounting records match physical reality, helping to detect errors or fraud in time.[6]​.

• - Reduce ordering costs. When ordering a batch of raw materials from a supplier, a cost is incurred for processing the order, tracking the order, and receiving the purchase in the warehouse. By producing a larger number of batches, larger inventories will be maintained, but fewer orders will be placed during a given period, thereby reducing annual ordering costs.[7]​.

• - Reduce costs due to missing materials. By not having material available in inventory to continue production or meet customer demand, costs are incurred. Among them, lost sales, dissatisfied customers, costs for delaying or stopping production. In order to have protection to avoid shortages, additional inventory, known as safety inventory, can be maintained.

• - Reduce acquisition costs"). In the purchase of materials, the acquisition of larger lots can increase raw material costs; however, smaller costs can be reduced due to quantity discounts and lower freight and material handling costs. For finished products, larger lot sizes") increase in-process and finished product inventories; However, average unit costs could be lower because machinery and technology costs are distributed over larger lots.

It is desired to reduce inventories because, as levels increase, certain costs increase, for example:

• - Storage cost. Among the costs incurred to store and manage inventories are: interest on debt, unused interest that would be earned on income, warehouse rent, conditioning, heating, lighting, cleaning, maintenance, protection, freight, receiving, materials handling, taxes, insurance and administration.

• - Difficulty responding to customers. The existence of large inventories in process clogs production systems, increases the time necessary to produce and deliver orders to customers, which decreases the ability to respond to changes in customer orders.

• - Cost of coordinating production. Large inventories clog the production process, requiring more staff to resolve traffic problems, resolve production congestion, and coordinate schedules.

• - Costs due to reduction in capacity. Materials ordered, held, and produced before they are needed waste production capacity.

• - Costs for defective products in large batches. When large batches are produced, large inventories are obtained. When a large batch is defective, large quantities of defective inventory are stored. Smaller batch sizes (and thus a reduction in inventory levels) can reduce the amount of defective materials.

Contenido

Los costos relevantes de los involucrados en la administración del desarrollo de los inventarios") son:.

Order cost

The cost generated by the activities carried out in a stock replenishment request is called "order cost", which may include, for example, the cost of paper, the cost of the telephone, the preparation cost and others.

Inventory storage cost

"Storage cost" is called "all the processes and activities carried out to maintain the order, good condition and existence of the inventory within the plant, including the cost of fixed assets of the product"), the cost of cleaning"), the cost of space").

Total inventory cost

The total inventory cost is the sum of the two previous costs: annual storage cost and annual ordering cost, according to the following formula:.

CT = total annual inventory cost.

Q= order size to replenish inventory, in units.

C= value of item handled in inventory, in $$/unit.

h= handling cost as a percentage of the item's value, percentage/year.

D= annual demand for items, which occurs at a certain constant rate over time, in units/year.

o= acquisition cost, in dollars/order.

When and how much are the questions on which stock management is based. In effect, if the inventory is replenished in short periods of time, the quantity ordered must be small, which reduces the cost of storage" but increases the cost of placing orders; if the inventory is replenished in long periods of time, the quantity ordered must be large, which reduces the cost of placing the order, but increases the cost of storage").

In inventory management there are inventory replenishment models that try to balance costs and reduce them as much as possible. With these models it is possible to know how much to order and when to order.

With fixed order interval models, an optimal fixed interval is determined for carrying out inventory reviews. Then each time an order is placed, stock is requested for the difference between some maximum and the quantity on hand.

POQ") determines the number of demand periods that will be covered by each order. This interval is calculated using the average demand and rounded to the next integer greater than zero. Each ordered quantity covers the projected requirements for the next interval with orders varying according to the requirements.

This algorithm is a heuristic approach to determining lot sizes that determines them by balancing ordering and storage costs. Selects the number of periods that should be covered by a replenishment order such that the accumulated storage costs barely exceed the ordering costs. Due to the discrete nature of requirements, an order size increases to the same extent that cumulative storage costs are less than or equal to the order cost. The goal is to determine lot sizes that include an integer number of periods.

This algorithm is similar to the PPA algorithm, except that instead of balancing cumulative storage and ordering costs, it balances incremental costs. The algorithm increases order sizes as incremental storage costs are less than or equal to order costs. The objective is to determine lot sizes that include an integer number of requirement periods. Similarly to the previous method.

Los siguientes modelos dan respuesta a la pregunta: ¿Cuánto pedir?

Economic Order Quantity (EOQ)

It consists of finding the point at which the costs of ordering the items and the costs of keeping them in inventory are equal. This is a method that does not give an optimal solution, but it is close to it.

Economic Production Lot (EPQ)

Items are produced and added to inventory gradually rather than in a single order. The EPQ model assumes continuous gradual releases to inventory (finite replacement rate) throughout the production period. With a finite replacement rate, the inventory level will never be the size of the production lot, since production and consumption occur simultaneously during the production period.

Silver and Meal Heuristics

Edward Silver") and Harland Meal") developed the Silver-Meal") heuristic model based on determining the average cost per period as the number of replacement periods increases. A replenishment order is placed when the first average cost increases. This method selects lot sizes that include an integer number of requirement periods such that the total relevant costs (storage and ordering costs) per period are minimized. This method guarantees a local minimum for the current order. Two situations in particular Where this algorithm does not work well are: (1) when the demand rate decreases rapidly over time and (2) when there are a large number of periods with zero demand.

Minimum unit cost

This method is similar to the Silver-Meal algorithm except that, instead of averaging costs across periods, it averages costs across units. This heuristic determines the average cost per unit as the number of periods in a replenishment order increases. An order is shipped when the average cost per unit first increases. The replacement period is reset and the procedure is repeated until lots are obtained in the time horizon.

The ABC" system is used to classify materials according to the economic value they represent in the inventory.

• - Materials A represent 75% of the inventory value. They represent only 20% of materials that must be in inventory.

• - B materials represent 20% of the inventory value and 30% of the materials in inventory.

• - C materials represent 5% of the inventory value and 50% of the materials in inventory.

With this system, it is deduced that it is most convenient for the materials that maintain a greater volume in the inventory to be those that represent the lowest cost.

Exceptions from the ABC system must be made for certain types of materials:.

• - critical materials for production.

• - materials with short storage life.

• - large and bulky materials.

• - bulky materials subject to theft.

• - Stock.

• - Inventory valuation.