Why aren't tags 57 and 5A returned with my EMV transaction?

There are three steps to an EMV transaction: Start, Authenticate, and Complete.

On each set, only a small subset of EMV tags are returned by default. 5A and 57 are returned after Start, but not Authenticate or Complete. If they auto-authenticate, they won’t see any of the tags from start, so they will never see tags 5A and 57.

With each API command of Start,Authenticate,Complete, there is a field to pass additional tags. If they pass DFEE1A, they can specify what tags they want returned after that step INSTEAD of the default set. So if they want to see tags 5A at 57 at the Authenticate step (or the Complete Step), they need to pass DFEE1A 02 5A 57, but remember this will ONLY return those two tags, which won’t be enough information. So they should pass DFEE1A XX 5A 57 <OTHER TAGS>.

Alternately, they can RetrieveTransactionResults AFTER any step to get what ever tags they like. So, they can just the default tags at Authenticate (which does not have 5A or 57), and then execute retrieveTransactionResults (5A57) to also get those.

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