Double-entry bookkeeping system
Double-entry bookkeeping, in accounting, is a system of bookkeeping so named because every entry to an account requires a corresponding and opposite entry to a different account. For instance, recording earnings of $100 would require making two entries: a debit entry of $100 to an account called "Cash" and a credit entry to an account called "Income."
The earliest known written description of double-entry accounting comes from Franciscan friar Luca Pacioli. In deciding which account has to be debited and which account has to be credited, the golden rules of accounting are used. This is also accomplished using the accounting equation: Equity = Assets − Liabilities. The accounting equation serves as an error detection tool. If at any point the sum of debits for all accounts does not equal the corresponding sum of credits for all accounts, an error has occurred. It follows that the sum of debits and the sum of the credits must be equal in value.
Double-entry bookkeeping is not a guarantee that no errors have been made—for example, the wrong ledger account may have been debited or credited, or the entries completely reversed.