I completely understand that issue I have customer's who forget the bills due

but knowing that upfront gives you an advantage if you know there going to be late either write in the contract" checks are due at completion or with in 72 hours of invoice" and by same contract late fee's are added on, When I have worked for attorneys my line 6 in my contract says payment with in 72 yours of invoice and any invoice not paid in that time frame incurs a penalty fee of 5 % of contract by day with your agreement to pay for all attorney fee's, private detective fee's and any cost to collect my funds are authorized

Not sure on the legality of that addendum to the contract but I have had attorneys at my office the following day ticked off at 7 am, but with check in hand lol and lets face it if your going to slow pay me,, I don't want your work any way. I think the best solutions is to get better clients and unfortunately you are not able to give new clients an idiot test if only we could huh but if there good customers that slow pay add a fee to help with your waiting on them with a rock clause of sorts