Performance ID number

Actually, ticket number would probably be a better option for this circumstance.  First, it’s a standard design element that you may already have on your ticket (and can add easily if you don’t).  And second, to return a seat on the web using the performance ID you also need the database ID of the seat being returned.  So you would have to also print that on the ticket or have your website look it up.  Generally speaking, if the constituent will be entering information to return a ticket, ticket number should be used.  But if they are selecting a ticket to return from a list of eligible tickets that your website provides to them, then performance ID and seat ID are used (as the API method that looks up tickets that can be returned provides those IDs).  For full details you (or your web team) see the API Documentation document, specifically the details for the ReturnTicket and GetReturnTickets methods.

Actually, ticket number would probably be a better option for this circumstance.  First, it’s a standard design element that you may already have on your ticket (and can add easily if you don’t).  And second, to return a seat on the web using the performance ID you also need the database ID of the seat being returned.  So you would have to also print that on the ticket or have your website look it up.  Generally speaking, if the constituent will be entering information to return a ticket, ticket number should be used.  But if they are selecting a ticket to return from a list of eligible tickets that your website provides to them, then performance ID and seat ID are used (as the API method that looks up tickets that can be returned provides those IDs).  For full details you (or your web team) see the API Documentation document, specifically the details for the ReturnTicket and GetReturnTickets methods.