Stop your Child Benefit
To stop your Child Benefit you can either:
You need a Government Gateway user ID and password to fill in the online form. If you do not have a user ID, you can create one when you fill in the form.
You cannot stop your Child Benefit if you’re using it to pay back an overpayment (or to pay back certain other benefits from another country).
Responsibilities after your Child Benefit stops
You must pay any tax charge owed for each tax year up to the date your Child Benefit stops.
Use the Child Benefit tax calculator to get an estimate of how much you may owe each tax year.
Even after your payments stop, you must report any changes in your family life that affect your entitlement to Child Benefit.