In a manual system, a trial balance summarizes accounts and compiles an income statement. A trial balance gives descriptions and final balances on all accounts in the general ledger.

In a computerized system, you can click the number on the income statement to verify the source of the number. This is known as "drilling down" to find the details of the number. This situation does not require a trial balance.

Suppose you see $1,350 in rent expenses for a January to March income statement. After clicking the amount, you may see something like this from the general ledger: