Have you considered doing payments every other week and issuing receipts to indicate that payment is due? Every other Wednesday, I fill out receipts for 2 weeks care and pass them out to clients. This is a gentle way to remind everyone that they owe me money more than actually providing them a tax receipt, since I also provide one in February for the full annual amount. I've found this to be an excellent way to let people know that payday is coming without actually having to chase anyone. In 13 years, though I've had a problem with a couple people, for the most part, it's made things much simpler and less awkward.