A method and system for aggregate registration and transparent data notification to services during IMS registration. A network entity, such as Serving Call Session Control Function (S-CSCF) may receive an aggregate registration request that includes a plurality of service identifiers and associated service-specific data sets. The aggregate registration request is sent by a user agent or other similar program on behalf of a user. The network entity then sends a notification to each particular service of the plurality of services, including in each notification the service-specific data set for the particular service. The user may thus supply service-specific data to each service during IMS registration, obviating the need for the user to directly and separately contact each service for the purpose of supplying service-specific data.