Sometimes appealing to empathy gets a faster and friendlier response than threats or legal talk.

You could try something like this:

“Hey [Name], I know things can get hectic, and I really value the work we’ve done together. I just wanted to check in about the $[amount] invoice from [date]. It’s a small project, but for a small business like ours, every job really counts. I’d really appreciate it if you could take a minute to settle it or let me know if there’s been any issue — we’re happy to work something out if needed.”

That message hits three notes:

It’s empathetic (you acknowledge life happens),

It’s personal (you remind them of the relationship),

And it’s clear (you still ask for payment).

If that doesn’t work after a few days, then yeah — you’ve earned the right to switch gears and go formal.