Refunds should take between 3-5 working days to be credited to your customer’s bank account.
Refunds for foreign currencies and international banks may take between 5 and 8 working days to reach the customer.
If the payment has been made via debit card, the money will be debited to the customer's bank account and if payment has been done using credit card, it will be debited to his Credit card itself.
The time depends on whether the 2 banks involved are the same or are different banks. It may take more time for international banks.