Your 10-class punch cards, on your phone
Each regular's classes left, taken off with one tap at the door instead of a hole punch.
Try the check-inThis is a trial on a made-up studio, so every client and class here is fictional.
Why the count goes wrong
A notebook or spreadsheet updated by hand is easy to forget, and then it shows the wrong number of classes left.
Moving your cards over
Add each regular by name and enter the classes left on their card: a 10-class card with 3 punches is 7. When they buy the next pack, add 5 or 10.
At the door
Tap their name and one class comes off. Tapped twice? Only one comes off. Wrong person? Undo gives it back.