1. A system, comprising: a reader device configured to electronically obtain an identifier for an item having a plurality of physical identifiers; one or more processors; and a memory coupled to the one or more processors, wherein the memory stores program instructions that when executed by the one or more processors cause the one or more processors to: receive, from the reader device within a materials handling facility, the identifier for the item, wherein the received identifier corresponds to one of the plurality of physical identifiers for the item; determine that the received identifier does not have a matching authoritative identifier on a list of authoritative identifiers; in response to determining that the received identifier does not have a matching authoritative identifier on the list of authoritative identifiers, send an indication that another identifier corresponding to another one of the plurality of physical identifiers should be obtained; receive the other identifier for the item; and to identify the item, determine that the other identifier matches one of the authoritative identifiers from the list of authoritative identifiers.