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

J63320

In early December I updated my Personal Tax Account with an estimate of the interest I will receive in 2025-26, because it will be less than I received in 2024-25. On Christmas Eve I received a letter from HMRC asking for details of all the interest I have received this year because, they say, their records show that I “have received £nnnn” which is the figure from 2024-25.

This is going to be fun because I (will) have had interest from around 15 accounts, some of which are now closed. Fortunately I have kept good records. 

RG2015

J63320 said:

In early December I updated my Personal Tax Account with an estimate of the interest I will receive in 2025-26, because it will be less than I received in 2024-25. On Christmas Eve I received a letter from HMRC asking for details of all the interest I have received this year because, they say, their records show that I “have received £nnnn” which is the figure from 2024-25.

This is going to be fun because I (will) have had interest from around 15 accounts, some of which are now closed. Fortunately I have kept good records. 

At least they got 24/25 correct, which is more than they did for me.

J63320

RG2015 said:

J63320 said:

In early December I updated my Personal Tax Account with an estimate of the interest I will receive in 2025-26, because it will be less than I received in 2024-25. On Christmas Eve I received a letter from HMRC asking for details of all the interest I have received this year because, they say, their records show that I “have received £nnnn” which is the figure from 2024-25.

This is going to be fun because I (will) have had interest from around 15 accounts, some of which are now closed. Fortunately I have kept good records. 

At least they got 24/25 correct, which is more than they did for me.

I’ve spent some time this morning getting the details together. The disadvantage of an online-only account is having to open umpteen files on my PC to find the one with the account number. I’ve overestimated the number of accounts I need to report on - only 10 have actually paid/will pay me interest this year. The form from HMRC has space for 4 - they clearly don’t expect people to be actively managing their savings.

RG2015

J63320 said:

RG2015 said:

J63320 said:

In early December I updated my Personal Tax Account with an estimate of the interest I will receive in 2025-26, because it will be less than I received in 2024-25. On Christmas Eve I received a letter from HMRC asking for details of all the interest I have received this year because, they say, their records show that I “have received £nnnn” which is the figure from 2024-25.

This is going to be fun because I (will) have had interest from around 15 accounts, some of which are now closed. Fortunately I have kept good records. 

At least they got 24/25 correct, which is more than they did for me.

I’ve spent some time this morning getting the details together. The disadvantage of an online-only account is having to open umpteen files on my PC to find the one with the account number. I’ve overestimated the number of accounts I need to report on - only 10 have actually paid/will pay me interest this year. The form from HMRC has space for 4 - they clearly don’t expect people to be actively managing their savings.

I have only ever reported the total of all of my accounts online.

I have always had to phone HMRC to report (or compare) each individual account.

RG2015

RG2015 said:

On 7 December 2025 HMRC issued my P800 for 2024/25 with an untaxed interest amount of £666. This figure was incorrect and I phoned them the next day.

We compared their actual figures with mine and discovered that they didn't have anything from RBS, Naitonwide and First Direct. The revised interest was £1,195 and their agent recalculated my P800 and we agreed my correct rebate. A new P800 appeared online the next day and I claimed my rebate. This appeared in my bank account on 12 December.

HMRC had already issued a revised tax code for 2025/26 on 4 December using the £666 in the calculation. I had expected this to be revised but as yet it has not.

I wondered if HMRC would be checking my figures or perhaps they are not bothered as the effect on my tax is relatively small.

I do find it odd that HMRC have a process for reporting untaxed interest and when it fails they are happy to rely on the clients figures.

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. Why have HRMC done this?

They have now used 3 different untaxed interest figures for my tax code for 25/26.

1. The actual for 23/24
2. My estimate for 25/26 given to them online on 30 Jan 2025
3. Their mistaken actual for 24/25 (£666)
4. My estimate for 25/26 given to them online on 30 Jan 2025.

The most recent one is the only week1/month1 code.

Dazed_and_C0nfused

RG2015 said:

RG2015 said:

On 7 December 2025 HMRC issued my P800 for 2024/25 with an untaxed interest amount of £666. This figure was incorrect and I phoned them the next day.

We compared their actual figures with mine and discovered that they didn't have anything from RBS, Naitonwide and First Direct. The revised interest was £1,195 and their agent recalculated my P800 and we agreed my correct rebate. A new P800 appeared online the next day and I claimed my rebate. This appeared in my bank account on 12 December.

HMRC had already issued a revised tax code for 2025/26 on 4 December using the £666 in the calculation. I had expected this to be revised but as yet it has not.

I wondered if HMRC would be checking my figures or perhaps they are not bothered as the effect on my tax is relatively small.

I do find it odd that HMRC have a process for reporting untaxed interest and when it fails they are happy to rely on the clients figures.

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. Why have HRMC done this?

They have now used 3 different untaxed interest figures for my tax code for 25/26.

1. The actual for 23/24
2. My estimate for 25/26 given to them online on 30 Jan 2025
3. Their mistaken actual for 24/25 (£666)
4. My estimate for 25/26 given to them online on 30 Jan 2025.

The most recent one is the only week1/month1 code.

The most common reason would be that the new tax code is lower than the previous one and using a non-cumulative basis (week1/month1) safeguards against unexpected amounts of tax being deducted the first time you are paid with the new code in place.

It is only temporary in the sense that it wouldn't be carried forward from one tax year to another.  Even if the code number remains the same for 2026/27 it would automatically revert to a cumulative basis.  You can read the P9X letter HMRC issue to employers and pension payers to see how that works.

I wonder if HMRC are as confused by your interactions with them as I am.  They have apparently used 3 different figures 🤔

1. The actual for 23/24

2. My estimate for 25/26 given to them online on 30 Jan 2025

3. Their mistaken actual for 24/25 (£666)

4. My estimate for 25/26 given to them online on 30 Jan 2025.

RG2015

Dazed_and_C0nfused said:

RG2015 said:

RG2015 said:

On 7 December 2025 HMRC issued my P800 for 2024/25 with an untaxed interest amount of £666. This figure was incorrect and I phoned them the next day.

We compared their actual figures with mine and discovered that they didn't have anything from RBS, Naitonwide and First Direct. The revised interest was £1,195 and their agent recalculated my P800 and we agreed my correct rebate. A new P800 appeared online the next day and I claimed my rebate. This appeared in my bank account on 12 December.

HMRC had already issued a revised tax code for 2025/26 on 4 December using the £666 in the calculation. I had expected this to be revised but as yet it has not.

I wondered if HMRC would be checking my figures or perhaps they are not bothered as the effect on my tax is relatively small.

I do find it odd that HMRC have a process for reporting untaxed interest and when it fails they are happy to rely on the clients figures.

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. Why have HRMC done this?

They have now used 3 different untaxed interest figures for my tax code for 25/26.

1. The actual for 23/24
2. My estimate for 25/26 given to them online on 30 Jan 2025
3. Their mistaken actual for 24/25 (£666)
4. My estimate for 25/26 given to them online on 30 Jan 2025.

The most recent one is the only week1/month1 code.

The most common reason would be that the new tax code is lower than the previous one and using a non-cumulative basis (week1/month1) safeguards against unexpected amounts of tax being deducted the first time you are paid with the new code in place.

It is only temporary in the sense that it wouldn't be carried forward from one tax year to another.  Even if the code number remains the same for 2026/27 it would automatically revert to a cumulative basis.  You can read the P9X letter HMRC issue to employers and pension payers to see how that works.

I wonder if HMRC are as confused by your interactions with them as I am.  They have apparently used 3 different figures 🤔

1. The actual for 23/24

2. My estimate for 25/26 given to them online on 30 Jan 2025

3. Their mistaken actual for 24/25 (£666)

4. My estimate for 25/26 given to them online on 30 Jan 2025.

@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!

poblomov

@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

RG2015

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.

Dazed_and_C0nfused

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.