An OPEX, from the English "Operational expenditures", is a permanent cost for the operation of a product, business or system. It can be translated as operating expenses, operating expenses, or operational expenses.

Its counterpart, capital expenditure (Capex), is the cost of developing or supplying non-consumable components for the product or system.

For example, the purchase of a photocopier involves capital expenses, and the annual consumption of paper, toner, energy and maintenance cost represents operating expenses. For larger systems such as companies, operating expenses can also include the cost of workers and installation expenses such as rent and services (water, electricity, etc.).

In business, an operating expense is a day-to-day expense, such as sales and administration, or research and development, as opposed to production, costs and pricing. In short, this is the money the business spends in order to convert inventory into throughput. Operating expenses also include an amortization of facilities and machinery used in the production process.

On an income statement, "operating expenses" is the sum of a company's operating expenses for a period of time, such as a month or a year.

In throughput accounting, the cost accounting aspect of the theory of limitations (TOC), operating expenses are spent on inventory money on throughput [1]. In TOC, operating expenses are limited to costs that vary strictly with the quantity produced, such as raw materials and purchased components. Everything else is a fixed cost, including labor (unless there is a regular and significant possibility that workers will not work a full-time week when they report on their first day).

In a real estate context, operating expenses include the costs associated with the operation and maintenance of a rental property.

Operating expenses include accounting expenses, licensing fees, maintenance and repair expenses, such as trash pickup, janitorial service, pest control, lawn care, advertising, office expenses, supplies, attorney fees and legal expenses, utilities, such as telephone, insurance, property management, including a resident manager, property taxes, travel and vehicle expenses.

Travel expenses are defined as those generated in the case of travel necessary for professional purposes.

For this purpose, "traveling" is defined as the simultaneous absence from residence and the usual place of work. It is driven by professional or company reasons and probably does not address the travelers' private lives, or concerns that only to a small degree. Travel expenses include travel expenses and fees, accommodation expenses, and additional expenses called for meals. For self-employed workers (contractors and independent workers), expenses consist of business expenses, leasing commissions, salaries and wages, and raw materials.