HMRC miscalculation of HICBC liability

Hello, I knew in October 2022 that I would for the first time exceed net income of £50k. That being so, I notified HMRC of cancellation of Child Benefit from then. For FY 2022-23 I received £942 of Child Benefit (2 children), having opted out in October 2022. My net adjusted income was £56513, meaning I had an entitlement to receive 35% of the total Child Benefit for the year. The total child benefit for the year would be approx. £1880. 35% of that is £658. As I received £942 of child benefit, I expected to be liable for £284 of HICBC (i.e. £942 received, less £658 entitlement). Instead, HMRC have calculated that I owe £612 for HICBC. The HMRC advisor I spoke to says this is because the HICBC is based on Child Benefit actually received for a year. But I have found guidance on HMRC website that says the HICBC will be equivalent to some/all of the Child Benefit that a person is entitled to receive. So my position remains that I was entitled to receive c. £1880 per year, and I remain entitled (taking into account income above the £50k threshold) to 35% of that amount, i.e. £658. How do I get this reflected in my self assessment tax return? I do not want to pay more than I am obliged to. Thanks.

Hi Catherine,
We would need to review your Self Assessment tax retrun to check the HICBC calculated. You can contact HMRC at Self Assessment: general enquiries.
Thank you.