Double-entry book-keeping

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 "Revenue."

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.

In the double-entry accounting system, at least two accounting entries are required to record each financial transaction. These entries may occur in asset, liability, equity, expense, or revenue accounts. Recording of a debit amount to one or more accounts and an equal credit amount to one or more accounts results in total debits being equal to total credits for all accounts in the general ledger. If the accounting entries are recorded without error, the aggregate balance of all accounts having Debit balances will be equal to the aggregate balance of all accounts having Credit balances. Accounting entries that debit and credit related accounts typically include the same date and identifying code in both accounts, so that in case of error, each debit and credit can be traced back to a journal and transaction source document, thus preserving an audit trail. The rules for formulating accounting entries are known as "Golden Rules of Accounting". The accounting entries are recorded in the "Books of Accounts". Regardless of which accounts and how many are impacted by a given transaction, the fundamental accounting equation A = L + C will hold, i.e. assets equals liabilities plus capital. Note that capital is at times, used interchangeably with owners' equity.

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