Is it harder to get VAT back if you use a credit card on purchases or should we use cash?

It should make no difference. Every time I've filed for a VAT refund, it came on my credit card within 2 or 3 months at most.

I thought in Ireland that you are required to use a credit card. Someone correct me if I am wrong.
At any rate, we used credit cards and our refund only took three weeks or so.

Shouldn't matter whether you pay with cash or credit card. The merchant will give you the VAT refund form either way.

It is definitely better to use a credit card if you plan on requesting a VAT refund. Then would you get a credit on your charge card account in a few weeks.

You can use cash of course - but then the refund comes as a check drawn in the currency of the country of purchase. A 10 euro or £10 check would cost more than that to cash in the States because of the bank charges at both ends.

Or you can get a cash refund right at the airport - but theyu administration/exchange charges are larger than a credit directly into your account.

So for VAT refund purchases, it is much better to use a credit card.

How do I get the VAT form?

You must get it from the merchant at the time of purchase. You turn it in after showing it and your receipt at the airport VAT desk at the airport before you leave.

sorry about all the typos in my original post

Make sure you have a copy of your passport with you, as the VAT form requires your passport number.

Don't forget that you have to ASK the stores for the form, which is sometimes filled in at the register and sometimes in a completely different area (so if you buy from more than one register in the store wait until you're finished and then do them all at once).

Also check with the merchants (who should have a brochure) and ask them if there are any in-town areas to get/apply for your refund. We generally just do it at the airport but I know at least in London there are areas in the center of town where you can drop off your form, which may be more convenient if you're in the area.

In France it makes a difference. Some will give you cash on the spot, but it'll cost you 5%. In other words, while some dept stores give a 17% VAT refund, if you get cash on the spot, you only get 12% refund.