Check for duplicate payments

To help ensure a merchant does not accidentally charge a customer twice for the same order, your application must check each payment response issues for the duplicate object. When a card with the last 4 digits is used for more than one payment in an hour, POTENTIAL_DUPLICATE is returned.

{
  "issues": {
    "duplicate": {
      "description": "POTENTIAL_DUPLICATE"
    }
  },
 ...
}

When this happens, the POS must prompt the merchant to verify the transaction details and give them the option to accept or refund the payment.