GOOGLE PLAY CARDS ARE A GREAT WAY TO BUY APPS AND MEDIA, AND REDEEMING THEM IS EASY
Google announced Google Play cards late last summer in the U.S., and have since been made available in Canada and the U.K. Of course, we all want them to be able to go global with the service, but there has been no word of when we can expect that to happen. In the meantime, if you're in a supported country, it's nice to know just how to apply the balance from a card to your Google account.
It's a pretty simple affair. You can find the gift cards themselves at retailers like Target or Walmart in the US and Canada, and Tesco and Morrisons in the U.K. They come in $10, $15, $25 and $50 denominations in North America, and £10, £25 and £50 in the U.K. You'll find them next to iTunes cards in most retailers, and you buy them like any other item off the shelf from the store. Once you get them home, adding the balance to your account is easy.
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REDEEMING ON THE WEB
You can apply the balance to your Google account (your Google Wallet account if you want to be specific) from your Android device or from any computer with a modern web browser. We'll look at redeeming the balance on the web first.
Simply fire up your web browser and point it at play.google.com/redeem. You'll likely be asked to authenticate by signing into your Google account, do that just like you would if you were accessing Gmail or any other Google service. You'll then be forwarded to the redemption page.
Next, take a coin of a sharp fingernail and scratch off the grey security paste covering the redemption code. It's just like a scratch-off lottery ticket, except you won't lose $2 while you scratch it. Once you've uncovered your redemption code, simply enter it into the text box marked with the word "code" on the right side of the page and click the Redeem button. You'll get confirmation that it was successful and you'll be able to use that balance to buy apps and media.
REDEEMING ON YOUR DEVICE
It's just as easy to redeem a gift card on your Android device through the Google Play app as it is from the web. Open up the Google Play application, and make sure you're at the main view where you can choose which Google Play store you want to visit. In the action overflow menu (those three buttons in the upper right), or the standard menu if your device has a dedicated menu key, you'll see the entry that says Redeem in the list. Tap it.
You'll need to be patient for a second as the app accesses your Google Wallet account, and then you'll be faced with a dialog to enter your redemption code. Scratch off the security covering over your card's code number, and type it in the text box that says "Enter code". With a tap of the green Redeem button you'll be set, and have the balance to spend in Google Play.
It's worth noting that Google Play balances on your Wallet account "cannot be redeemed for Android app subscriptions, magazine subscriptions, or hardware and accessory purchases", but will work just fine for apps, music, videos or books.
Source : http://www.androidcentral.com