What is the matching concept in financial accounting?

The Matching Concept:

A significant relationship exists between revenue and expenses. Expenses are incurred for the for the purpose of producing revenue. In measuring net income for a period, revenue should be offset by all the expenses incurred in producing that revenue. This concept of offsetting expenses against revenue on the basis of "causes and effect" is called the Matching Concept.

The term 'matching' means appropriate association of related revenues and expenses. In matching expenses against revenue the question when the payment was made or received is 'irrelevant'. For example if a salesman is paid commission in January, 2001, for sale made by him in December, 2000. According to this concept commission expense should be offset against sales of December 2000 because this expense is incurred for producing revenue in December 2000. On account of this concept, adjustments are made for all outstanding expenses, accrued revenues, prepaid expenses and unearned revenues, etc, while preparing the final accounts at the end of the accounting period.