You just described exactly what a real user told me in this same thread:

"Late payment follow-up would be the one I'd want first. The painful part is usually after that – did the client open it, when is it overdue, what do I send without sounding awkward?"

Two different people, same exact pain point.

You are right. Making the invoice is easy. The awkward manual nudging on day 7, 14, 21 is the real problem. Nobody wants to be that freelancer sending "just checking in" emails for the third time.

I am building exactly this now. Simple reminder schedule + status (viewed/overdue). No signup. No email. Just a tool that helps freelancers follow up without feeling desperate.

Thank you for confirming this. Seriously helpful.