In a checking account, which field must be unique to keep transactions separate when reconciling accounts?

The field that must be unique to keep transactions separate when reconciling accounts is the Transaction ID. This is because every transaction in a checking account is assigned a unique Transaction ID that allows for precise tracking and identification of each individual transaction.

When reconciling accounts, it is essential to differentiate each transaction from all others to ensure that errors can be identified and corrections can be made accurately. The unique Transaction ID serves this purpose as it provides a specific reference for each entry, making it easier to align records with bank statements and internal accounts.

In contrast, while other fields like the Account Number or GL Account are important for identifying the source of transactions or categorizing them, they may not individually provide the unique identification necessary for reconciling each transaction. A Customer ID is useful for identifying transactions related to specific customers, but it does not uniquely differentiate each transaction on its own within the checking account context.