I redeemed an ITunes card at Christmas but on my account it doesn't look like any of my purchases were credited to the ITunes card and there is not a balance showing. How do I determine if any of my purchases were charged to the ITunes card?
Unless you still have the emailad receipts for your purchases then there isn't any way of seeing via iTunes how an item was billed - items charged to an account's balance will have 'Billed To : Store Credit' on the receipt.
The only other way is to compare your purchase history on your account to the charges on your credit card statements.
To view your purchase history : log into your account on your computer's iTunes via the Store > View Account menu option, you should then see a Purchase History section with a 'see all' link to the right of it. Click on that and you should then see a list of your purchases .
Question on redeeming ITunes cards
