A method for providing a confidence score for a seller in an online marketplace includes: storing account profiles, each including one or more unique account identifiers for one or more online marketplaces; storing activity data entries, each including data for transactional activity in an online marketplace including a marketplace identifier, two or more transacting account identifiers, and activity data; receiving a confidence request that includes a specific account identifier and marketplace identifier; identifying a specific account profile that includes the specific account identifier; identifying a set of activity data entries where a transacting account identifier matches a unique account identifier in the specific account profile; determining a confidence score for the specific account profile based on the activity data included in the identified set of activity data entries; and transmitting the confidence score in response to the received confidence request.