I waited 19 days to chase a late retainer payment because I did not want to seem pushy

My best client went quiet on a $1,400 retainer invoice and I just let it sit.

It was due on the 1st. By the 5th I had drafted a follow up email twice and deleted it both times. I told myself they were busy, that chasing would make me look desperate, that one late payment from a good client was not worth an awkward conversation. So I kept posting their content like nothing was wrong and checked my bank balance a lot.

On day 19 I finally sent the shortest version I could write. Something like: just flagging invoice 104 is still open on my end, let me know if you need anything from me to process it.

They replied in under an hour. The invoice had gone to their old ops inbox when their office manager left. Nobody had seen it. It was paid the next morning.

That one stung a bit. The delay was never a money problem or a respect problem. It was an inbox problem, and my worrying about seeming pushy turned a two day admin fix into almost three weeks of me quietly stressing about rent money.

So I built the follow up into the boring part of the job instead of leaving it to courage. Now every retainer goes out with a note the day before it is due. If the due date passes, I follow up the next morning, still friendly, just a flag. Around day 3 I ask what their accounts person needs from me, a PO number, a different format, whatever, because that question has fixed it more than once. Day 7 gets firmer and mentions the late fee that is already in the contract. And the contract now says work pauses at 14 days overdue, which I have never actually had to use since writing it down.

The part I did not expect: clients do not seem to mind any of this. If anything the organized ones respect it. The reminder the day before reads like a service, not a chase, because half the time they were about to forget.

How long do you wait before you chase a late one? And do you put the pause clause in writing or just handle it case by case?