A method for customized authentication of a subaccount includes: storing an account profile, wherein the account profile includes a structured data set related to a transaction account including a plurality of subaccounts, each subaccount including an associated account number, authentication rules, and authentication values; receiving a transaction message related to a payment transaction, wherein the transaction message includes a transaction account number and authentication data; identifying a specific subaccount in the account profile where the included associated account number corresponds to the transaction account number; and authenticating the authentication data based on the authentication rules and the authentication values included in the identified specific subaccount.