Do you think this is a good idea to do with my babys child trust fund ?
You have to put the voucher into a Child Trust Fund Account. There are comparison websites that will tell you the best interest rate. You can put it into a CTF share account, which doesn’t guarantee interest or the capital, but over the 18 years it will probably out perform a savings CTF account. I put my daughter’s voucher into the Yorkshire BS Child Trust Fund account as it had the best interest rate, but you have to check the interest monthly as they won’t necessarily inform you of any change. You don’t have to deposit any more money into the account, however some providers provide incentives for setting up a direct debit, such as store gift cards.