An Identity and Access Management Service implements persistent source values PSVs) for assumed identities. A source value (e.g., an original identifier of an entity) is persisted across assumed identities, facilitating identification of entities (users or applications) responsible for actions taken by the assumed (e.g., alternative) identities. The Manager receives a request to assume an identity. The request includes the entities current credentials and a PSV. The current credentials are authenticated and a persistent source value policy may be relied on to determine whether and/or how to grant the assumed identity. The PSV may be copied from credentials in the request in order to be included in the credentials for the requested identity that the Manager provides in response to the request. Use of the requested credentials, including the PSV, to access services or resources may be logged, the logs including the PSV from the request to assume the identity.