I overpaid a credit card for $100 and canceled it because it was extra.

That overpayment stuck. But they'd canceled it so they couldn't refund it. But I couldn't use it because it was canceled. It was connected to me as a negative debt but couldn't be activated, modified, or removed.

Every month, then, I'm reminded of this -$100 bill that, without any action from me, is paid promptly on time.

Fast forward 30 years.

It's been a great credit bump for me, these 30 years of -$100 owed and paid every month. I'm told it still reflects well on my credit, because it's SO long-term and steady. They asked whether I wanted it removed, now, because they finally can, and I asked for it to be left on.

Neat.