What bookkeeping system ensures that debits always equal credits?

The bookkeeping system that ensures debits always equal credits is double-entry bookkeeping.

In this system, every transaction is recorded in at least two accounts: one or more debits and one or more credits. The total debit amount must equal the total credit amount, keeping the ledger and the accounting equation in balance. For example, buying equipment with cash debits the equipment account and credits cash; borrowing money debits cash and credits a loan liability.

Double-entry bookkeeping is built around the equation assets = liabilities + equity. It does not mean every account has equal debit and credit balances individually. Instead, the combined entries for each transaction balance across the ledger. A trial balance later lists account balances in debit and credit columns as a check.

The method is associated with Renaissance commerce. Luca Pacioli described the Venetian system in his 1494 work Summa de Arithmetica, although double-entry records existed before his publication. Single-entry bookkeeping lacks this same complete two-sided structure.