Originally Posted by Former Teacher:
I agree with the PP that people forget their checkbook or other some lame excuse. IMO, if you make Monday your payday: then inform them that effective Monday evening at pickup if there is no payment (late fees included) then they may not come in the door Tuesday.
IME: Mondays were the worst day for being hectic and having forgetful parents 
THis is what I have in my contract as well. Either pay on am or pm pick up, otherwise late fees will be added, and need to be paid in full, otherwise I will not provide care on Tues. am.