Pay people back before they have to ask. Making them ask is a cost you’re charging them.

Debts stop being about money the moment somebody has to chase them. Asking is awkward, so people put it off, and while they are putting it off they are thinking about it, which means you borrowed money and handed them a small ongoing job. Paying first removes both at once, and the speed is the part that gets remembered.

Settle what you owe this week without being reminded, even partly, with a note saying when the rest comes. If you are short, say so before the date rather than after it. Hold the same standard for the small amount you borrowed at lunch, because that is where the reputation forms.