Nintendo is Issuing Credit for Adding Money to Your Wii U eShop Account
From now till July 28, you’ll receive bonus credit whenever you add $50 or more to your wallet.
$50 dollars will give you a $5 credit and $100 will net you $10. Once you add the funds, you will be mailed a promo code that you need to redeem in order to get your credit.
So if you plan on picking up Pikmin 3 or an eShop buying binge, add to your wallet and save some cash!