The cashier who let you come back with the missing dollar trusted a kid she didn’t know. Pay it forward.

Letting somebody come back later with the missing money is a decision to trust a stranger, made in a few seconds, with nothing to back it up. The amount was small and the gesture was not, because the message was that you would be treated as honest until proved otherwise. Most people get the strict version of the rules. Being handed the lenient one is luck and generosity arriving together.

Pass it along in whatever form you can afford. Cover the shortfall for someone ahead of you, lend without a reminder, give the benefit of the doubt to a person obviously having a bad day.