Debits and credits in double-entry bookkeeping are entries made in account ledgers to record changes in value resulting from business transactions. A debit entry in an account represents a transfer of value to that account, and a credit entry represents a transfer from the account. Each transaction transfers value from credited accounts to debited accounts. For example, a tenant who writes a rent cheque to a landlord would enter a credit for the bank account on which the cheque is drawn, and a debit in a rent expense account. Similarly, the landlord would enter a credit in the rent income account associated with the tenant and a debit for the bank account where the cheque is deposited.

Debits and credits are traditionally distinguished by writing the transfer amounts in separate columns of an account book. The use of separate columns simplifies calculation of the balance for the account. First the debit column is totaled, then the credit column is totaled. The account balance is calculated by subtracting the smaller total from the larger total. Only one subtraction is needed, simplifying calculations before the availability of computers.

Alternately, debits and credits can be listed in one column, indicating debits with the suffix "Dr" or writing them plain, and indicating credits with the suffix "Cr" or a minus sign. Despite the use of a minus sign, debits and credits do not correspond directly to positive and negative numbers. When the total of debits in an account exceeds the total of credits, the account is said to have a net debit balance equal to the difference; when the opposite is true, it has a net credit balance.

Debit balances are normal for asset and expense accounts, and credit balances are normal for liability, equity and revenue accounts. When a particular account has a normal balance, it is reported as a positive number, while a negative balance indicates an abnormal situation, as when a bank account is overdrawn. In some systems, negative balances are highlighted in red type.