You Can Merge Your Nintendo Switch, 3DS and Wii U eShop Credit
They're separate, but it's easy to fix.
The Nintendo Switch is finally out! We have them in our hands. One quick trip to the Nintendo eShop shows that the Switch has another new eShop separate from the 3DS and Wii U one. This also means your accounts for each are also separate. But that can be easily fixed with Nintendo's new system called a Nintendo Account.
It's simple, and the Nintendo-approved method of moving forward with a new joined account. Go to your Nintendo Account page and choose to merge the two wallets. Simple right? You can do this with both Wii U and 3DS accounts.
This new Nintendo Account lets you pick a new user ID, similar to how other consoles do it. Adding friends still requires a friend code, but more methods are rumored to be on the way. We know the Virtual Console wasn't included at launch but is planned to be added in the (hopefully) near future.