Fees that add themselves up
The group knows how much is due and by when. The amount owed sits beside the member's name, a payment is one tap, and the reminder is sent for you.
The app in use, recorded.
A group carries one fee rule: the amount, whether it is due per session, week, month or year, and the deadline — a fixed date, the fifth of every month, the first Tuesday of every month, or every Tuesday. That is all. There are no invoices, and none are needed: what a member paid is booked, and what they owe is worked out again on every read from the rule and the day they joined.
Two numbers, not one
The balance is what is already due: on the first of the month, the whole month. The overdue amount is only what is past its deadline — that is the red tag on the member list and at check-in. On the deadline day nobody is overdue yet; the day after, they are. An overpayment stays a credit and never turns into a debt.
Paying at the desk
On the Fees page the Overdue switch in the filter shows who needs a word. One tap on the member, the amount is already filled in, and the Pay button makes the red tag disappear. A mistyped payment is deleted by an admin.
One reminder
Whoever misses a deadline and has an e-mail address gets a message — exactly one per missed deadline, not one per day. You write the text; the name, group, amount and deadline are filled in. Anyone who would rather not get them is muted with a switch.