Late. That's how :/

Invariably we have to spend a lot of time sending emails chasing late payments, and sometimes making phone calls. They always eventually pay, but it always takes a ridiculous amount of energy to get to that point.

Oh, and US customers (we are based in the UK) most often still pay by cheque (or 'check', if you are American :), which take weeks to clear and usually involve high processing fees. On the occasions where US customers pay by bank/wire transfer, they sometimes do so while specifying that we also pay their side of the transaction fees. Bad practice, and very irritating :/