Understand late penalty fees

Hello, Tax year 2022-2023 was my first time submitting a self-assessment and I totally missed the deadline as I was not aware of this (which is my bad of course). I received a letter of HMRC on 1st April 2024, informing me about a late submission penalty fee of £100. Same day (1st April 2024) I: 1) Submitted my self-assessment for tax year 2022-2023 2) Paid the late submission penalty fee of £100 My self-assessment return resulted to an outstanding tax fee that I needed to pay (which is understandable). However, I'm also now being charged for: 1) 30 days late payment fee of £147 2) Accruing late payment interest from 31st Jan to 3rd April I do not understand where these fees are coming for, especially the 30 days late payment one. I paid my overdue tax the same day that I submitted my self-assessment, so I do not understand why a 30 days late payment fee shows up. I appreciate the late submission penalty fee, but since I've paid the overdue amount same day this was generated, I cannot understand those 2 items. Can somebody explain where these come from and if I should appeal against them or not?

Hi,

The balancing payment due date for the 2022 to 2023 Self Assessment was 31 January 2024. As you paid after this date then a late payment penalty and interest have been charged.
If you want to appeal the late payment penalty details on how to do this:

Check when to appeal a Self Assessment penalty for late filing or late payment

Thank you.