Underpaid Tax Calculations

Hi, In the recent self-assessment done for 2022-23, I was shown an underpaid tax from prior years. This cannot be correct because I have paid additional amount in Jan 2023, as part of self assessment done then, covering any shortfall in the tax paid by my former employer. I would like to get details or calculations to understand the basis of the underpaid tax. It seems to me my Jan 2023 payment is not accounted for. How do i get the underpaid tax calculations? thanks.

Hi akash gupta,
You will need to contact HMRC to review the underpayment from previous tax years:
Self Assessment: general enquiries
Thank you.