Underpayment - Confused and need help!

Hi, I received a letter from HMRC advising I had underpaid tax in 2022 by £1565. I had failed to noticed my tax code had changed after my firsts months pay in a new job and I was moved from 1250L to BR W1/M1. Tried ringing HMRC numerous times, waiting 40+ minutes and usually get cut-off. Submitted a complaint on 22nd June but not had a response. Managed to get through to someone yesterday on the phone and now I'm totally confused, we seemed to be on different pages in different books. Following the letter, my tax code was changed to 905L for 2023, reducing my tax free allowance by nearly £4000 in order to collect the £1565 owed. Checking my tax payments from April 2023 onwards (3 payroll runs so far), I've now paid a total of £6303.40 in tax. By comparison, for Jan, Feb and March which fall into 2022 Tax year, I paid a total of £4235.60. An increase of £2067.80. In my head, I assumed I have now paid the underpayment of £1565. Here's where I now become further confused: - HMRC said on the phone yesterday that I had only paid 3 amounts towards the underpayment. £1565 /12 = £130.41. Multiply this by 3 = £391.25. - I explained that I paid over £2k more tax so far in April, May and June compared to the previous 3 months but was told this was because of my bonus and this isn't calculated until the end of the year. - HMRC then said this was because of a 'potential' underpayment. I argued that the letter I received hadn't said it was potential. I was advised it was because of a missing figure from a P11D from my previous employment, and, I needed to contact the previous employer to confirm that figure. I asked what evidence HMRC would need to add the missing P11D details and they said me verbally telling them would be fine. - I contacted previous employer today who advised I was never entitled to any benefits (i.e. Company car / medical benefit) and therefor no P11D exists for me. - I asked HMRC can I just make a payment for the underpayment, as all I want is for my tax code to be back to normal, and they said they can post me a letter with a payment slip on. They said the process of making a payment and updating their end usually takes a couple of months........ - I suggested, at the current rate I'm being taxed, by the end of this year I will have paid nearly £8000 more tax than last year, if you take away the underpayment of £1565 then they would owe me £6500 (I'm approximating figures here!). I got advised if I was unhappy with the process to write to 11 Downing Street. Any advice would be appreciated? What's happened to the extra £2067 I've already paid this year, why can't that be used for the underpayment? Why would it take a couple of months to process a one off payment? Can my tax code be reverted and they issue me with a bill rather than changing my allowance? Thanks 


Name removed admin .

Hi Doug Blake,
We would need to see your record to fully explain the underpayment and what the extra amounts taken in your tax code mean for the overall position
If we are collecting the underpayment from the earlier year in your tax code, we can't remove this until you make the payment in full for the underpayment.
Once this has been done we would remove it from the tax code and issued a new code.
This new code would cause any amount you have paid since April towards the underpayment to be refunded when the code is applied.
We can't take into account the amount paid through your code as the tax you have paid during the year is not confirmed until the end of the year and we do a tax calculation. If there is a figure in your tax code for this 'P11D' figure this will need to be removed and you will need to contact the helpline again to ensure that is removed.
That may be causing you to pay more tax than you should:
Income Tax: general enquiries
Thank you.