One rule and one rule only.
If they owe you for the last clean, and you are due to clean them in the next week, they arnt customers!
We dont allow even one clean to go overdue. 5 Days, payment needs to be in. 7 days later, if still no payment, they are put on hold, and a letter goes out. 30 days late, well they are cancelled, letter goes out threatening civil action and we no longer accept them as future customers.
There are so many willing people to pay ontime, your wasting your time with non payers, and they are taking advantage of you.