Most businesses maintain a record of all transactions based on the double-entry bookkeeping system. However, many smaller businesses maintain only a single-entry system that records the "bare-essentials." In some cases, only records of cash, accounts receivable, accounts payable and taxes paid may be maintained.
Single-entry systems are used in the interest of simplicity. If a double-entry system is needed, then the services of a trained person are often required.
According to the U.S.A. Internal Revenue Service:A single-entry system is based on the income statement (profit or loss statement). It can be a simple and practical system if you are starting a small business.
Additionally, in the U.S.A. stated: