Appeal on interest for late payment on account for self assessment 2023/2024

Hi, I wanted to get help on something.
I applied for a relief on my payment on account for 23/24 tax year in July 2024 because I did not have the income to pay for this at the time.
My self employed income fluctuates throughout the year being a photographer, some seasons are more busy than others.
I filled in my self assessment in November 2024 and I am now being charged for interest for late payment on account from 31st Jan 2024 and 31 July 2024. 
I am not sure to understand why am I being charged on these periods,
My understanding was that payments on account were meant to decrease the amount owed to HMRC at the end of the tax year deadline (i.e 31 Jan 2025).
I could not pay the bill before but will be able to clear it in full at the end of Jan, how do I appeal for this interest payment charge?
I have never missed any payments in the past to HMRC since 2018 that I am self employed, any help on that matter would be greatly appreciated.
Thanks,
Mickaël

Hi Mickael Malaper
Please see guidance at: Understand your Self Assessment tax bill: Payments on account.
You can also find out information, along with progress of your form/payments credited by creating accounts in:
• your personal tax account
• the official HMRC app
Thank you
 

It sounds like you reduced your 23/24 payments on account below the total amount of tax you were actually finally liable for in 23/24 - however that isn't allowed. If you do it anyway, the reduction below your actual tax liability is undone, and you are held to be late paying the amounts of the payments on account from when they were originally due. It's a misunderstanding to think the 31st January of the following year deadline can be applied to your entire tax bill once payments on account have been issued. Essentially, the problem is that rather than reducing payments on account to avoid paying tax which will only be refunded later (allowed), you used the reduction to optimise your cash flow to defer paying tax actually due (not allowed). By the time of the second payment on account for 23/24, in July 2024, the 23/24 tax year is already finished, so you should have received all of the income on which you are being taxed at that point - and also enough information to calculate your total tax due for 23/24 to know how much, if any, you can reduce payments on account without penalty. If you have cash flow difficulties with paying the tax from the income on which it arose, https://www.gov.uk/difficulties-paying-hmrc may be relevant.