Before computers were in common use, bookkeeping was done by an actual bookkeeper. This person kept a company's day-to-day financial records by manually recording every business transaction into a journal. The journal entry included the date, the name of the accounts to be debited and credited, and the amounts. The bookkeeping process further required that all journal amounts be rewritten in (or "posted" to) the company's general ledger and subsidiary ledger accounts.

With the writing and rewriting of so many amounts (as well as the manual calculations) it was realistic to assume that some errors would occur in the bookkeeping process. This potential for errors created the need to periodically "prove" that a company's accounts were "in balance," meaning the total of the debit balance accounts was equal to the total of the credit balance accounts. An internal document called a trial balance was designed to give that proof. If the trial balance did not balance, the bookkeeper had to go back, transaction by transaction, to find and correct the cause of any disparity. Once the trial balance was in balance, the bookkeeping phase was completed and the "books" were turned over to the company's accountant for the preparation of financial statements.