Test deposit mechanisms used by financial institutions to link accounts are used to identify undisclosed accounts associated with users of a data management system. The potential existence of undisclosed accounts is determined based on the assumption that the presence of test deposit transactions in user account data is a strong indication that an undisclosed user account exists. Using this assumption, transaction data from user accounts disclosed to a user data management system is scanned to identify test deposit transactions listed in the transaction data. If test deposit transactions are identified, the user of the data management system is queried regarding the existence of the undisclosed user account. If the user confirms the existence of the undisclosed account, the formally undisclosed account is added to a set of disclosed user accounts with the data management system.