A computer system is presented for facilitating user enrollment at service providers, particularly with respect to storage and retrieval of user attribute information within a federated environment at entities that manage such information as a service. One domain can inform other domains of identities of service providers that are to be associated with a user, thereby enrolling information about the user at those domains. In addition, an enrollment operation can be invoked by a first service provider through a second service provider such that the user becomes enrolled at a third service provider. During an enrollment operation, information about multiple service providers may be associated with a user, and these service providers may be prioritized. The user may be provided an opportunity to reprioritize the service providers during the enrollment operation so that the service providers are subsequently contacted or used in a particular priority order.