transfer money from child to parent account

you can indeed transfer money from a parental account to a child account, can be done accidentally too, not sure if there is a way to transfer back as child account cannot transfer money.

My son wants to buy the Call of Duty and he redeemed his xbox gift card to his child account and when he goes to order it sends me an email and asks me if I allow it and when I say allow it asks how i want to pay. How do I pay for this with the money
he uploaded today

The funds should show as his Microsoft account balance. That is the payment method you would need to choose. If he's trying to purchase one of the Call of Dutys for the 360, he would need to do so from a 360 console.

Hello Noah,

Unfortunately, the money on an account cannot be transferred, at least currently, between accounts.

Here we have information for Adding Funds to a Child Account for full details on how an account
may garner money for usage on the Microsoft store.

We hope this information helps and wish you the best!

You can't transfer licenses or content from one account to another.

The accounts Parent / Child are separate accounts. The parent account just manages the child account.

The child account will remain a child account until the birth date that was used for that account reaches the age of 18.