In common usage, an expense or expenditure is an outflow of money to another person or group to pay for an item or service, or for a category of costs. For a tenant, rent is an expense. For students or parents, tuition is an expense. Buying food, clothing, furniture or an automobile is often referred to as an expense. An expense is a cost that is "paid" or "remitted", usually in exchange for something of value. Something that seems to cost a great deal is "expensive". Something that seems to cost little is "inexpensive".

In accounting, expense has a very specific meaning. It is an outflow of cash or other valuable assets from a person or company to another person or company. This outflow of cash is generally one side of a trade for products or services that have equal or better current or future value to the buyer than to the seller. Technically, an expense is an event in which an asset is used up or a liability is incurred. In terms of the accounting equation, expenses reduce owners' equity. The International Accounting Standards Board defines expenses as

...decreases in economic benefits during the accounting period in the form of outflows or depletions of assets or incurrences of liabilities that result in decreases in equity, other than those relating to distributions to equity participants.

Bookkeeping for expenses

In double-entry bookkeeping, expenses are recorded as a debit to an expense account (an income statement account) and a credit to either an asset account or a liability account, which are balance sheet accounts. An expense decreases assets or increases liabilities. Typical business expenses include salaries, utilities, depreciation of capital assets, and interest expense for loans. The purchase of a capital asset such as a building or equipment is not an expense.

Cash flow

In a cash flow statement, expenditures are divided into operating, investing, and financing expenditures.

• Operational expense (OPEX)—salary for employees
• Capital expenditure (CAPEX)—buying equipment
• Financing expense—interest expense for loans and bonds

An important issue in accounting is whether a particular expenditure is classified as an expense, which is reported immediately on the business's income statement; or whether it is classified as a capital expenditure or an expenditure subject to depreciation, which is not an expense. These latter types of expenditures are reported as expenses when they are depreciated by businesses that use accrual-basis accounting, which is most large businesses and all C corporations.