Well, in fairness I do think there's a bit of difference between a basket of shopping and being short 20p for milk.
The monetary value perhaps, but in the moment they were at my desk, they promised they would return in a short time period with the money ... they may have had every intention of coming back, but then got home and the cat was on fire and then they had to go hunt for the moon on a stick for their child's school project and the shopping totally slipped their mind.
I don't know any of this, all I know is that someone promised to return with money and never came back.
At what point should I apply a cut off? In my supermarket you can get a pint of milk for 40p, so if youre 20p short then you're short 50% of the price. what about if you want some bread for £1 but you only have 50p, should I let you owe me that too, it is the same % after all ...
Also what monetary value should I let slide and at what point do I say no? So you're 20p short, no problem, what about 50p? 75p? £1? Where is the cut off of going from "Sure, don't worry about it!" to "Sorry, you can't afford this, please comeback when you have the correct amount" and why is it the customer who decides?