The same receipt, twice: catching reused payment proof

Why verification alone does not catch it

Verifying a receipt answers one question: did this transaction happen, and for how much. It cannot answer whether the transaction was meant for you, or whether somebody else already accepted it, because the bank has no idea what you sold.

That gap is what reuse exploits. A customer pays one shop, keeps the confirmation, and presents it at a second shop an hour later. Both verifications succeed. Both sellers see a genuine receipt for the right amount. One of them is not getting paid.

Closing it

Two checks, and neither needs anything clever.

1. 1.Keep the reference of every payment you accept, and check a new one against that list before you accept it. A verification service that records your own history does this for you; a notebook does it too, more slowly.
2. 2.Check the receiver on the verified receipt against your own account, every time. A reused receipt usually names the first shop rather than you, which gives it away immediately if anyone looks.
3. 3.Check the timestamp against the moment the customer is standing in front of you. A receipt from three days ago being offered as payment today deserves a question, even if it is genuine.

The receiver field is the one people skip

Of the three, the receiver check catches the most and costs the least. It needs no history, no records and no memory: the verified receipt says who was paid, and either that is your account or it is not.

It is skipped because the status is the thing that feels like the answer. A receipt that says the transfer succeeded reads as good news, and the eye stops there. Train whoever is at the counter to read one line further down.