Will HMRC check the untaxed interest that I have given them?

RG2015

Dazed_and_C0nfused said:

RG2015 said:

poblomov said:

@Dazed_and_C0nfused

Many thanks for your response.

Sorry I have confused you by my interactions with HMRC, but I am happy to explain

1. HMRC used my actual untaxed interest for 23/24 for my first tax code on 20 January 2025.
2. This was incorrect so I used their online facility to give them my estimate.
3. They duly updated my tax code on 22 Feb 2025.
4. They issued my P800 for 24/25 on 4 Dec 2025 and updated my tax code for 25/26.
5. I told them the untaxed interest used was incorrect and they re-issued my P800
6. They then issued a new tax code for 25/26 using the first interest figure I gave them in January 2025.  

So I have had 2 interactions with them, giving them my interest estimate for 25/25 and correcting their mistake for my actual interest for 24/25.

In fact the 24/25 interaction has had no effect on my tax code as they have not used this figure for any tax code.

So much for me confusing HMRC, they have done this all by themselves!

It's worked how it should as far as cumulative or month 1 basis is concerned.

The 25/26 code issued in Feb 25 was to be used from April 25 so issued on a cumulative basis

The first 25/26 code issued in Dec 25 deducted less tax than the Feb 25 code so was issued on a cumulative basis

The later 25/26 code issued in Dec 25(?) would deduct more tax than the earlier Dec one so is issued on a month 1 basis (in case the earlier Dec code has been or is used for the Dec payroll before the new code is received)

Ideally HMRC's systems should be prevented from replacing your 25/26 estimate with the supposed 24/25 figure as the former is likely to be a more accurate estimate of the actual 25/26 interest, but they aren't

poblomov 

Thank you for this which does explain the week1/month1 code.

So as it stands, Apr to Dec was about right and then the new code in January will give me a small windfall.

Feb and Mar will be back to normal, but I guess I will end up underpaying tax for the year.

They also made a mistake last year which resulted in an overpayment. I was not able to get this corrected and did not get my rebate until December 2025. Swings and roundabouts then, and I will be paying the balance some time in the future, probably next year.

I don't think you've understood this.  In a previous post yesterday you said this,

I have just got a revised tax code for 25/26 and it is a Week 1 / Month 1 code. I have just looked this up and aparently this is a temporary code.

As the code has been issued on a non-cumulative (week1/month1) basis each pay day from now on will be looked at in isolation.  So if you get the same pension each month the tax will also be the same, certainly until 5 April 2026.

Thanks again, and I am trying really hard to understand this.

My tax code for Apr to Dec 2025 was 253M.

The code for Jan 2026 was 294M and my tax deducted is already showing on my PTA online and has been applied cumulatively.

The code now is 253M week1/month1 and I assume this will apply for Feb and Mar 2026.

I have assumed that the monthly tax deducted in Feb and Mar 2026 will be the same as the tax deducted in each of the months Apr to Dec 2025. Is this assumption incorrect?

poblomov

RG2015 said:

Thanks again, and I am trying really hard to understand this.

My tax code for Apr to Dec 2025 was 253M.

The code for Jan 2026 was 294M and my tax deducted is already showing on my PTA online and has been applied cumulatively.

The code now is 253M week1/month1 and I assume this will apply for Feb and Mar 2026.

I have assumed that the monthly tax deducted in Feb and Mar 2026 will be the same as the tax deducted in each of the months Apr to Dec 2025. Is this assumption incorrect?

If your monthly gross PAYE income from this payer is the same throughout the year, Feb and March should be the same as April to December.

If you don't mind trying to call HMRC, you probably could ask them to issue the current code on a cumulative basis to claw back the Jan windfall.

Or you can just wait for it to be dealt with when they do the tax year calculation.

RG2015

poblomov said:

RG2015 said:

Thanks again, and I am trying really hard to understand this.

My tax code for Apr to Dec 2025 was 253M.

The code for Jan 2026 was 294M and my tax deducted is already showing on my PTA online and has been applied cumulatively.

The code now is 253M week1/month1 and I assume this will apply for Feb and Mar 2026.

I have assumed that the monthly tax deducted in Feb and Mar 2026 will be the same as the tax deducted in each of the months Apr to Dec 2025. Is this assumption incorrect?

If your monthly gross PAYE income from this payer is the same throughout the year, Feb and March should be the same as April to December.

If you don't mind trying to call HMRC, you probably could ask them to issue the current code on a cumulative basis to claw back the Jan windfall.

Or you can just wait for it to be dealt with when they do the tax year calculation.

Thanks, but I think I will let things run their course. I’ll be up by about £60 this year and will probably end up payng it through my 27/28 tax code.

RG2015

They have changed my tax code again this morning. It is now 253MX but as far as I can see this is no different to 253M week1/month1.

I wonder if this is down to HMRC having a different figure for my actual untaxed interest for 24/25? They said they would replace their “actual” with my actual for 24/25. Thus not fully accepting it, although they did use my figure to recalculate my 24/25 P800. Hence the reason for my original question whether they would check my actual for 24/25.

Dazed_and_C0nfused

RG2015 said:

They have changed my tax code again this morning. It is now 253MX but as far as I can see this is no different to 253M week1/month1.

I wonder if this is down to HMRC having a different figure for my actual untaxed interest for 24/25? They said they would replace their “actual” with my actual for 24/25. Thus not fully accepting it, although they did use my figure to recalculate my 24/25 P800. Hence the reason for my original question whether they would check my actual for 24/25.

The X and week1/month1 elements are not part of your tax code, they signify the basis of operation the code (253M) is to be operated.

So absolutely no change, it was, and still is, on a non cumulative basis.

RG2015

Dazed_and_C0nfused said:

RG2015 said:

They have changed my tax code again this morning. It is now 253MX but as far as I can see this is no different to 253M week1/month1.

I wonder if this is down to HMRC having a different figure for my actual untaxed interest for 24/25? They said they would replace their “actual” with my actual for 24/25. Thus not fully accepting it, although they did use my figure to recalculate my 24/25 P800. Hence the reason for my original question whether they would check my actual for 24/25.

The X and week1/month1 elements are not part of your tax code, they signify the basis of operation the code (253M) is to be operated.

So absolutely no change, it was, and still is, on a non cumulative basis.

Thanks again.

So HMRC show my tax code as 253MX but the X is not part of my tax code.

Every day is a school day!