There are cases when the terminal prints out receipt and there is a space on receipt for signature and the customer needs to sign the receipt and then terminal at some point is asking on screen for the terminal user to confirm if the signature on receipt is valid or not, if terminal user confirms then sale was authorised, if declines or does nothing then the sale will be cancelled.
The flow of what happens during a swipe and signature payment:
Cardholder swipes card, auth request is sent to host.
Host responds with auth response, if it is approved then the merchant copy is printed.
The cardholder is expected to sign on the merchant copy of the receipt.
The terminal asks the merchant whether the signature matches with what is on the card.
a) If the merchant presses yes, then an authorised cardholder receipt is printed.
b) If the merchant presses no, or after 90 seconds when the transaction times out, the terminal will then print out a declined copy of both merchant and cardholder receipt.