First, you are only allowed to buy 2 bags per passport. The tax refund. They will give you the necessary documents and before leaving the Europe, at the airport, you can get your cash rebate for 10% or ask them to credit the rebate to your credit card for 12%. But with my experience, rebate was paid to my credit card at 10% also and it took around 2 months. So my suggestion is just opt for the cash.