The life of a business unit is indefinite as per the going concern concept. To determine the profit or loss of a firm, and to ascertain its financial position, profit & loss accounts and balance sheets are prepared at regular intervals of time, usually at the end of each year. This one-year cycle is known as the accounting period. The purpose of having an accounting period is to take corrective measures keeping in view the past performances, to nullify the effect of seasonal changes, to pay taxes, etc.
Based on this concept, revenue expenditure and capital expenditure are segregated. Revenues expenditure are debited to the profit & loss account to ascertain correct profit or loss during a particular accounting period. Capital expenditure comes in the category of those expenses, the benefit of which will be utilized in the next coming accounting periods as well.
Accounting period helps us ascertain correct position of the firm at regular intervals of time, i.e., at the end of each accounting period.