Methods, systems, and apparatus include computer programs encoded on a computer-readable storage medium for crediting an entity for a conversion. A method includes: providing an interface to an entity; receiving transaction information from the entity through the interface; creating a token; providing the token to the entity; storing the transaction information in association with the token in a first log; receiving from the entity a user identifier associated with the transaction along with the token; associating the user identifier with the token in a second log; determining a linking between impressions and conversions including using the token to determine a relevant user identifier and transaction details, and using the relevant user identifier to locate prior impressions made to the user; and debiting a content sponsor associated with the prior impression, and crediting a publisher that published the impression and the entity, when a linking impression and conversion is located.