Simple Assessment Letters for Unpaid Tax

Around 1.4 million individuals are soon expected to receive Simple Assessment Letters from HMRC as part of their compliance work for the 2024/25 tax year.

These notices are designed to collect income tax that HMRC believes has not been paid. The Simple Assessment system is intended to reduce the need for full tax returns in straightforward cases.

If you’ve already received one of these letters, it’s important to understand what it means and how to respond, especially if you already file a Self-Assessment tax return.

What Is a Simple Assessment?

Simple Assessment is a tax calculation issued by HMRC when they believe you owe additional income tax. It is typically used if your income exceeds your personal allowance and has not been fully taxed through PAYE or, reported via Self-Assessment.

Using information from third party sources, such as employers, banks and investment platforms, HMRC calculates what they believe you owe and sends you a notice to pay.

Who Is Likely to Receive a Letter?

You may receive a Simple Assessment if HMRC believes you have received untaxed or under-taxed income, including:

• Interest from savings or dividends above your allowances

• Earnings from second jobs or freelance work

• Overclaimed tax-free allowances (such as Marriage Allowance)

• State or private pensions not fully taxed through PAYE

What Should You Do?

If you receive a Simple Assessment letter, you must either:

• Pay the full amount shown in the notice, or

• Contact HMRC to arrange a payment plan

The payment deadline is 31 January 2026. You can pay via the HMRC website, by bank transfer, or by cheque.

What if I think it’s wrong?

If you believe the figures are incorrect, you have the right to:

• Query the notice within 60 days of the issue date

• If your query is unsuccessful, appeal within 30 days of HMRC's response

It’s essential to deal with these notices promptly to avoid penalties, interest, or enforcement action.

What if I already submit a Self-Assessment tax return?

If you already file a Self-Assessment tax return, there is a risk that the same income may be taxed twice. It’s important not to assume the Simple Assessment is correct, or that it replaces your normal filing.

In these cases, you should get in touch with us as soon as possible as our tax team can review your notice, check for any inaccuracies and ensure you are not overpaying tax.

We are here to help so please do not hesitate to get in touch.

Written by: Ffion Bainbridge