Booked the way an accountant would
A gift voucher isn’t a sale until it’s spent: the money is held as owed (Gift Vouchers), and moves to sales when the voucher pays for something. Points spent are a sales discount, so you can see what the programme costs you. Lay-by deposits are held as the customer’s deposit, and the sale, its VAT and the stock movement happen when the goods are collected.
Store credit for a return works like a voucher for that customer. Nothing is guessed, and nothing needs fixing at month end.
Know your regulars at the counter
Search by name or phone and the till shows their points, what they owe and their credit limit. Add a new customer on the spot with a name and a number, and they start earning straight away.