If you get your tax refund in cash, there is no "fee". You get the entire VAT back. BUT if you don't submit the stamped custom form, they will recharge your credit card. If you return the fee to the card, there is a processing fee. I believe it is not different from merchants charging you a transaction fee for using your credit card (If you are american, you can thank Obama for that, prior to him merchants were not allowed to charge the fee to you)