Two bookkeeping methods in most common use today are the single-entry bookkeeping system and the double-entry bookkeeping system. Single-entry bookkeeping is adequate for many small businesses; it uses only income and expense accounts recorded primarily in a revenue and expense journal. In the double-entry system, at least two accounting entries are required to properly document each financial transaction. These entries may be recorded to asset, liability, equity, expense, or revenue accounts.
The primary bookkeeping record in single-entry bookkeeping is the cash book, which is similar to a checking account register (in UK: cheque account, current account), except all entries are allocated among several categories of income and expense accounts. Separate account records are maintained for petty cash, accounts payable and receivable, and other relevant transactions such as inventory and travel expenses. To save time and avoid the errors of manual calculations, single-entry bookkeeping can be done today with do-it-yourself bookkeeping software.
A double-entry bookkeeping system is a set of rules for recording financial information in a financial accounting system in which every transaction or event changes at least two different nominal ledger accounts.