If you need to make an appointment for a past date, on the pet card, click on Historical appointment.

This will allow you to choose past dates.  Then you can go to that date on the schedule and check the pet in/out.

You will be able to put the date of any payments that have been made and confirm any outstanding balances by hitting Pay at Pickup.

Outstanding invoices you may have before PawLoyalty:  You can add the appointments but you can only go back to the first date PawLoyalty was created for you.

To make the invoice read correctly if you cannot enter in all the correct dates (i.e. you started using PawLoyalty on 10/1 but you need to add an appointment/invoice for 9/15), you can adjust the final invoice and leave a note on the profile as to the pending invoice.