I agree and it's totally unenforceable anyway, unless clearly stated in a written agreement / contract they have signed..Can’t see people paying £3 fine and keeping you on tbf. If like you say you’re in the early stages of your business and every penny counts I think you might find you’ll be losing customers faster than you get them. Yes, you can suspend cleaning if they haven’t paid but fining them would be a no no in my book.
I don't know if you ever visit the other forum - it's like Jackanory meets La La Land at times with a fave philosophy r.e. bad payers of "drop 'em and replace with 2 new better customers". What nonsense. As I felt obliged to point out once to a regular user of this phrase, by definition he should have a round twice as big and more than twice as profitable on that basis.
The real world doesn't work like that.
Don't let people take liberties but show a bit of tolerance while you build a round and could be legitimate reasons why they haven't paid you or just forgot.
And no point making demands you can't enforce cos you'll just look a plonker and lose their custom.