V bucks purchase to my son

Consumables like Fortnite V-Bucks have to be purchased by the account that is supposed to use them.

Unfortunately, there is no way to transfer consumables to a different account. While it is possible to buy a game and some DLCs that your son can play thanks to the Home Console setting that shares your game purchases with the first console you set up with
your account, consumables can't be shared to a console.

Therefore your son can't see the V-Bucks in his account, as the V-Bucks are stored on your account, and not shared to the console.

In order to get your son V-Bucks, you would have to buy him a currency gift card, that your son then redeems, and with which he can then buy V-Bucks for himself.

If you buy v buck under any account they will go there no one is going to send you a code unless you buy them at walmart or amazon and they do send you a prepaid code

Unfortunately when purchasing a virtual currency like V-Bucks, they are placed onto the purchaser's account. This in large part is to help prevent fraudulent purchases and currency trading. Sadly we are unable to assist with refunds on these forums but
if you reach out to the MS Customer Support Team they should be able to assist in this matter further.

Yeah, when you purchase games or dlc or consumables (V-bucks), they download on the console for the account that purchased them, no codes are given.

Consumables usually are not refundable, but you can try from here
https://support.xbox.com/en-US/billing/xbox-subscriptions/digital-goods-subscriptions-refund

For purchasing for your son, you are better off purchasing a Xbox gift card for him, and redeem the code on his account, then he will be able to purchase v-bucks without using credit card or money from your account.

if you buy them from the store you won't get a code. To ask a refund go to
xbox.com/refund