To pay the charge, a person has to register for Self Assessment and fill out a Self Assessment tax return.
Wealth management group Royal London warned the tax charge may put people off claiming the support, which means people miss out on the potential benefits for their state pension, if there is a non-working parent.
Claimants with children under 12 may be able to get National Insurance credits (NI) to cover any gaps where they are not paying contributions while caring for the child.
A year of NI credits will cover the same amount of contributions as would be paid if a person was working and paying into the system, which goes towards their state pension.
