What is Refund?
A refund returns money to a customer for a cancelled or returned order, processed back through the original payment method.
Refunds to cards and UPI typically take several working days to appear, which is worth stating explicitly to the customer — most "where is my refund" queries are simply impatience with bank timelines.
Check whether your gateway returns its original processing fee on a refund. Many do not, meaning a refunded order costs you money even though no product was sold.