Hi warman,
Where a child gets more than £100 in interest from money given by a parent.
The parent will have to pay tax on all the interest if it’s above their own Personal Savings Allowance.
The £100 does not include money given by grandparents, relatives or friends; or in a Junior ISA or Child Trust Fund.
How you break this down to identify the parents element is up to you.
SAIM2430 - Interest: taxation of interest: children's accounts
Thank you.