Watch out for multiple Simple Assessment letters

In October, HMRC published details in Agent Update 136 about the issue of Simple Assessments for 2024-25. This confirmed that Simple Assessments which include savings interest for 2024-25 would be issued between October 2025 and March 2026.

On 1 November, ATT Technical Officer Helen Thornley talked to Paul Lewis on Radio 4’s MoneyBox to explain why some taxpayers may receive more than one Simple Assessment and what they need to watch for.

What is Simple Assessment?

Simple Assessment was introduced in 2017 as a way of collecting tax from individuals with relatively straightforward affairs, but who have untaxed income and would otherwise need to be in self-assessment.

Simple Assessment is the reverse of more familiar self-assessment.

Under self-assessment, the taxpayer gathers their details together, completes a tax return (usually online or using software) which calculates their tax and submits it to HMRC.

Under Simple Assessment, HMRC uses the information it receives from third parties including banks and building societies, employers and pension providers to calculate the individual’s tax bill and then sends it out for them to check.

Originally a limited number of taxpayers were moved from self-assessment to Simple Assessment, with the focus on two groups:

• pensioners with tax to pay that couldn’t be collected from their state pension, and
• employees whose tax bill on benefits in kind was too large to be collected via their PAYE code.

These days, Simple Assessments are used much more widely, with 1.32 million issued for the 2023/24 tax year.

Part of the increase has been due to greater numbers of savers with interest in excess of their Personal Savings Allowance, meaning they have tax to pay.

Rather than bring all these savers into self-assessment in line with legislation, HMRC’s guidance says that an individual with untaxed interest from savings (and no other reason to be in self-assessment) only needs to come into self-assessment if their interest exceeds £10,000. Otherwise, their tax will be collected via either the Simple Assessment process or an adjustment to their PAYE code.

Why might some people get two Simple Assessment letters in 2024-25? 

HMRC tell us that the majority of people who receive a Simple Assessment for the 2024-25 tax year will only get one letter. But, as HMRC only started including savings interest when calculating Simple Assessments from October onwards, it might be that some people who have already had a Simple Assessment for 2024-25 will receive a second one if HMRC identifies that they have more tax to pay.

For example, Alison received a Simple Assessment in July 2025 to collect tax on her pension income from 2024-25. The computation was issued at that point as the information HMRC received in previous years suggested that Alison was unlikely to receive enough interest to need to pay tax on it. Now that HMRC has received details of Alison’s actual interest from her bank, they can see that her savings interest was higher in 2024/25 and that tax is going to be due, so another assessment will be issued. 

It should be noted that HMRC receives significant volumes of bank interest and it takes time for them to process and match this data to taxpayers.

I have received two Simple Assessments, what should I do?

The key point for those who receive more than one letter is that a Simple Assessment always shows the total tax due for the year. The assessments do not take into account any payments that have been made following earlier letters.

If someone receives more than one Simple Assessment in respect of the same tax year, they should deduct anything they have already paid from the amount showing as owed in the second letter.

For example, Ajay receives a Simple Assessment in July 2025 showing an amount due of £400 for the 2024-25 tax year. He pays that in August. In November 2025, he receives an updated Simple Assessment showing that his total tax for 2024-25 is £1,000. Ajay should deduct the £400 he has paid, and pay over the balance of £600.

Before making any deductions of payments, it’s important to make sure that the payment made earlier relates to the same tax year as the latest Simple Assessment that has been received. Otherwise there is a risk of underpaying tax.

Simple Assessments for 2023-24 were issued until March 2025, so an individual who receives a Simple Assessment for 2024-25 now and remembers paying some tax in April or May 2025 (say) should check if the earlier payment relates to 2024-25 or 2023-24. Only earlier payments for 2024-25 should be deducted from an updated 2024-25 calculation.

For example, Alan received a Simple Assessment in March 2025 showing an amount due of £300 for the 2023-24 tax year. He paid that (late) in August. In November 2025, he receives a Simple Assessment showing that his total tax for 2024-25 is £1,000. Alan needs to pay the full £1,000 as his earlier payment relates to a different tax year.

What happens if a taxpayer overpays their Simple Assessment?

If an individual receives more than one computation for the same tax year, and pays the full amount due on both the first and second letter, it is likely that they will have overpaid.

HMRC tell us that if this happens, the taxpayer will need to call HMRC to request a refund.

Can taxpayers pre-empt their Simple Assessment by providing their savings income via their Personal Tax Account (PTA)?

We have been asked if taxpayers could ‘assist’ the process of generating a Simple Assessment by providing their data via the Personal Tax Account (PTA). This does not work.

Simple Assessments are based on the data HMRC receives directly from the banks. It’s not possible for a taxpayer to trigger - or pre-empt - this process by manually entering their interest details in their PTA.

However, providing interest figures via the PTA during the course of the tax year can help to ensure that the taxpayer receives more accurate PAYE coding notices to help HMRC collect the right amount of tax due from employment or pension income. This reduces the chance of a Simple Assessment being needed after the end of the year.

LITRG guides

For further details on Simple Assessment, the Low Incomes Tax Reform Group (LITRG) have a helpful guide aimed at the general public.