I had a client that's a broke ass meth clinic charity once over pay my invoice. I always submit the backup invoices when I give you a bill, so you know what I'm billing you for other than my direct services.

Their accountants paid my bill, and paid me for the backup bills.... that weren't made out to them or on my letter head.

I had to call the CEO and explain to them how they drastically overpaid me and that I'd be cool if they just short paid the following invoice to balance things out.

Can't imagine how much they've paid out erroneously.... makes me think twice about donating to them tbh. Good cause, questionable management it appears.