There is a button to do returns.
1. You can search the order by reference or by invoice number.
2. Open the product list in the order.
3. Check the product/s to return.
4. Now you have two options
4.1. You can generate a voucher.
4.2. You can add the return in a new order.
4.2.1. You can do the return in cash.
4.2.2. You can generate a discount in a new order.