The below are the best expalined terms on Void, Return and Reversals in credit cards domain.
What’s the difference between Reversal, Refund/Credit and a Void?
If your customer changes their mind on a product/service that same day and you hadn’t settled or batched your terminal yet, you would want to do a REVERSAL.
If it was after you settled or batched you would do a REFUND.
At the end of the day, you print a detail report and see that there is an error with a transaction, or you decide you don’t want to process that particular transaction; you then would also do a REVERSAL which is the same thing as a VOID to remove that transaction before you settled or batched.
Technically, after the required update to your terminal is completed, REVERSALS and VOIDS will do the same thing. Ref:Here