Change to tax code - Child benefit deduction incorrect

I recently had a message into my HMRC account informing of a change to tax code. I went to take a look and upon checking “How did we calculate this” section the deduction due for child benefit is listed at £2529, almost double what the online calculator suggests. What has gone wrong here?

Hi,

We would need to access your record to review and update your code.

You can contact our Income Tax team below.

Income Tax: general enquiries

Thank you.