Which type of ledger summarizes all accounts in a subsidiary ledger?

The correct answer is the controlling account. A controlling account is used to summarize the total balances of all accounts within a subsidiary ledger. For example, in accounts receivable, the controlling account will reflect the total amount owed by all customers, while the individual customer accounts within the subsidiary ledger will provide detailed information about each customer's balance.

This structure allows for efficient management of financial data, as it simplifies the reporting process. Instead of analyzing numerous individual accounts, accountants can review the summary in the controlling account, which facilitates easier identification of trends and outstanding amounts, while still having the detailed data accessible if needed.

The other types of ledgers mentioned do not serve this specific summarizing function. The general ledger contains all accounts for the business, including asset, liability, equity, revenue, and expense accounts, but does not exclusively summarize subsidiary accounts. The subsidiary ledger contains the detailed individual accounts themselves, rather than a summary. A department accounting system organizes accounts by department but does not inherently summarize all subsidiary ledger accounts.