The headline advantage of a junior ISA is that interest or investment returns are income tax free. However, most children will not pay tax on their income anyway, so you’re better off going with the best rates you can find. For savings, this is often via a children’s savings account rather than a junior ISA account.
There are some exceptions to this:
If your child already earns an income
If your child is earning an income, then they have a personal savings allowance that lets them earn up to £1,000 a year in interest without paying tax. But if they’re a higher-rate or additional-rate taxpayer, this allowance tapers away – eventually to nothing. If your child is earning more than the allowance in interest, for instance on savings built up over their whole childhood, an ISA might therefore be more tax efficient.
If they’ll earn more than £100 a year in interest from money gifted from parents or step-parents
Money that’s gifted from parents or stepparents has slightly different rules to savings gifted by other family members or friends.
Any cash in normal non-ISA savings accounts that earns more than £100 in interest per year will be taxed at the parent’s marginal rates. If the parent is still within their personal savings allowance, and the child’s savings don’t breach this, then the money is still tax free. However, once that limit is breached, then the whole savings pot interest will be taxed at the parents’ rate.