There is one way to check the balance of an iTunes gift card. The most common way is to redeem it in the iTunes store. But what if you want to just check the balance before you give it as a gift, and you’re not sure what the balance is?
Thanks to dabbara, there is an answer for how to check the balance of an iTunes gift card without redeeming it:
Look up the Support contact # from below link. For US – 1-800-275-2273
Explain the issue, and they will connect you to iTunes support center.
Associate here can look up the value on the card and if it has been activated or not, when you provide the PBHxxxxx or GCAxxxx at the left bottom of the card.
Well, I did contact support by email and provided the GCAxxxx code at the bottom left corner of the iTunes gift card. The reply did not confirm the amount on the gift card, but it did confirm the card was active and redeemable:
I’ve reviewed the code you have provided, and found that your iTunes Gift card is active and ready to be redeemed.
check balance on Apple Store Gift Card
To check Apple Store Gift Card balance, this URL https://secure1.store.apple.com/shop/giftcard/balance will look it up, after you login with an apple.com or iCloud account. This only checks gift cards for Apple Store and not iTunes.