Pay-as-you-go (or PAYG) passes allow a customer to check into the location even if they don't have a valid and unused pass. Depending on how you configure their pass, they would pay based on the total time they access the location or a fixed price. PAYG passes otherwise operate in the same way as standard time passes.
How to set up a pay as you go pass
You can select a pass to be sold to contacts and members individually in settings. For example, you may have a different price for contacts and members when they use the PAYG system.
PAYG settings (found in settings menu under Check-in settings)