Child benefit tax charge

Last year I earned 62k. I have done self assessment and was given a new tax code for this year of S815L. The deductions on my account are shown as £4050 for child benefit. When I talked to HMRC they have explained that although I owe them £2240 (or similar amount for child benefit received for 2 kids for previous year), the deduction is higher for them to be able to retrieve the whole amount. However, in April I have earned around 3.5k and on my May payslip with new tax code I have earned only 3.2k. The difference in tax which I paid is £285. I still do not get it. I owe £2240, my salary is less £285 each month which would be £3420 a year. Do I miss something?

Hi,
We would not be able to confirm what is in your code without viewing it. The deduction of £4050 would result in you paying 40% tax on that figure.
If you are unsure over the code please contact our helpline so that we can view the code and advise accordingly:
Self Assessment: general enquiries
Thank you.