I agree with Caddyshack. I have a few that seemingly "forget" to send payment, some of them two months worth, and then I call them or send them a reminder letter. Payment is usually made quite promptly at that point. Another thing that I do is if I have a customer that missed last months payment, I reprint the invoice and send two of them, and the one that was from the month prior I will stamp with a PAST DUE stamp. It's red and stands out. I don't ad a late fee, unless it is a customer worth losing. Now, on that note, I do have two customers that have not paid from services back in February and March. I have added late fees for all the invoices unpaid and sent them an other than pleasing letter. I have received a response from one and she is making arrangements to pay(allegdedly), the other, still nothing. It sucks when you lose out on money, but when you get down to brass tacks, for example, one of the customers I'm speaking of owes me $210. For the work we performed, it cost me maybe $40 (fuel, labor for 1 employee, time, equipment wear and tear, etc). So am I really out $210? No, I'm only out my expenses, it still sucks, but that will lessen the pain when you look at it that way. Good luck!