Until the child is 18?
When my kids were born we opened a junior saver for them, with me as the linked adult. We put a monthly amount in there as well as birthday and Christmas money. About 2 years ago we also opened a junior ISA and put some of the money in there. As interest rates went up, we put more and more in. And now only a small amount remains in the savings account. DS wanted to use his Christmas and birthday money recently to buy himself something (he's 8, this is the first time he's wanted something specific with his money).
I went to the savings account but there wasn't enough so planned to take a small amount from the ISA and found I couldn't! Was really really surprised. I obviously missed it when signing up. I had assumed that you could remove it, but with a tax implication (to stop adults using them to avoid tax) and we'd factored that in.
Obviously the solution now is for all birthday and Christmas money to go in to the saver (which I have instant access to) and leave the ISA for later.
But AIBU to not have realised?
I also know this is a first world problem and we're lucky to have money to put aside for the kids.