Answered by Shaykh Faraz Rabbani
Answer:
An amount that is customarily considered so insignificant that it would be ignored by the seller (which would depend on the type and size of the sale) does not have to be repaid. Otherwise, it must be repaid. This should be done as soon as reasonably possible, such as the next time you go to the store or pass by the area. If you die before repaying but had the determination to repay, then it is hoped that Allah will wipe such a debt away.
And Allah alone gives success.