Late penalty for a payment plan

I had a large SA for year ending 5th April 2022 which I couldn't afford to pay in one lump sum. I contacted HMRC as soon as I was made aware of the amount and I was placed on a payment plan for 12 months. I made the final payment on 22nd November 2023. This was agreed with HMRC and I paid the amount due each month on time with no late payments. I've now received a late payment charge which is completely unexpected as this tax bill was dealt with in agreement with HMRC. I've appealed but am still waiting on an answer and I just wondered if anyone knows what the potential outcome might be. Thanks

Hi leo1790,
You will need to contact HMRC to check on the appeal:
Self Assessment: general enquiries
Thank you.