transfer gamer tag to new Microsoft account?!

So I make a new microsoft account and transfer the harp one to it, then I can move the gamer tag to my new hotmaill?

On the contrary to what the others have mentioned changing the Microsoft account associated to the gamer tag automatically transfers all Microsoft Points and purchases, ETC to the new Microsoft account.

If you want the gamer tag you can change the Microsoft accounts around. However you will lose all achievements etc from the other account. You'll need to make a new email with Microsoft transfer your old profile to that one then transfer your old email to
the new profile with the desired GamerTag. Otherwise you'll need to change the gamertag on the account with the gamer tag you want then change it to the gamer tag you want on the account you primarily use. Changing your GamerTag costs $10 per switch. So all
and all it'll cost you $20. Good luck my friend.

I see the problem here....

If your son has been playing on your account, then I'm afraid it's impossible to transfer the gamer-tag over. If you have created a new account for him to use under your account, then he will have to start again with a new one. All the game progressions
will also need to be started from scratch.

You could try changing your own gamer-tag so it with free it up for him to use, but you still won't be able to transfer anything else.

You see, the details follow the Microsoft Account, not the gamer-tag.

Sorry....

Sorry to hear that you're having issues transferring the account. As you can see by the link below it is true that you cannot have another billing account associated with it.

support.xbox.com/.../switch-gamertag-to-different-microsoft-account

I'm not entirely sure why this is. Perhaps you could try posting to @xboxsupport on Twitter or contact Phone Support for your region for more information on that barrier.