Comment by tacostakohashi

This is totally correct, and something that took me a long time to learn.

Doing lots of slowly escalating "check-ins" and "reminders" means you are owning the problem, not the other party, and you're teaching them that every time they do nothing, they can expect another "reminder" or escalation that is not much firmer than where they are today. They become like the frog that gets boiled in slowly increasing water temperature.

Instead, I've found it much more effective to have only a small number of very clear interactions. Step 1) ask nicely - say what you need, when you need it - "payment is due in 14 days". Send approximately _one_ "first and final friendly reminder". That's it - if it doesn't work, and the 14 days has come and gone, then switch immediately into thermonuclear asshole mode - call them, show up at their office, hand it over to a lawyer/debt collector, etc, etc. It works best to a clear, contrasting, binary distinction between "asking nicely" vs "not nicely", good cop / bad cop, so that the transition is very obvious and gets a reaction.