I have a customer £20 a time. Hadn't seen them until the fourth clean and then she wrote me a cheque for £80. Neither of us batted an eyelid.
I have another customer that owed 4 x £8 and so I missed her out next time but caught her in on collecting night. I said it may be best to stop cleaning them to allow her to catch up paying. She paid £20 and now owes £12. She still wants them done but will wait until she's in the clear.
I have other customers that owe me £8 and I've dropped them and waived the money.