Key takeaways
- An HMRC nudge letter is a One to Many letter: one standard message sent to many taxpayers, which HMRC's Compliance Handbook says is not a compliance check.
- If you correct an error after a nudge letter, HMRC is likely to treat the disclosure as prompted, so the minimum penalty for a careless error rises from 0% to 15% of the extra tax.
- For deliberate errors the minimum penalty rises from 20% to 35%, and for deliberate and concealed errors from 30% to 50%.
- You can amend a Self Assessment return online within 12 months of the filing deadline, so a 2024/25 return can usually be changed until 31 January 2027.
- Errors in older years go through HMRC's digital disclosure service, or the Worldwide Disclosure Facility if they involve offshore income or assets.
- HMRC can normally assess 4 years back, 6 years for careless errors and 20 years for deliberate ones.
- HMRC's list of genuine contact, updated 27 October 2026, confirms 2026 letter campaigns on the High Income Child Benefit Charge, CIS discrepancies and missing VAT and Corporation Tax returns.
An HMRC nudge letter asks you to check one part of your tax affairs because HMRC holds data suggesting something may be missing. It is not an investigation, and you do not always have to reply. But if you find an error and correct it after the letter, HMRC will usually treat the disclosure as prompted, which raises the minimum penalty.
What is an HMRC nudge letter?
A nudge letter is HMRC’s informal name for a “One to Many” letter. HMRC’s Compliance Handbook at CH600110 describes the approach as sending “one standard message to many customers” to encourage compliance, and states that “a One to Many approach is not a compliance check”.
The same letter goes to everyone who matches a pattern in data HMRC already holds. It can come by post, email, text or through your personal tax account, and can go to you, your agent or both.
Which campaigns is HMRC running in 2026?
HMRC lists genuine campaigns on its page to check genuine HMRC contact, last updated on 27 October 2026. Compliance campaigns on that page include:
| Campaign | Contact window | Channel |
|---|---|---|
| High Income Child Benefit Charge | 6 July to 31 December 2026 | Letter, text |
| CIS discrepancies on Self Assessment returns | 10 August to 31 December 2026 | Email, letter |
| CIS incorrect rates on monthly returns | 7 October to 7 November 2026 | Email, letter |
| VAT missing return | From 10 August 2026 | Letter, text, email |
| Missing Corporation Tax return | From 16 November 2026 | Letter, phone, text |
The page also lists undated campaigns on cryptoassets and investors in offshore funds. Separately, HMRC is writing to people with significant control of companies about their 2025/26 returns; see HMRC letters to PSCs. The list is not complete, so a letter on another topic can still be genuine.
Do you have to reply to a nudge letter?
Not always. A nudge letter uses no formal legal power, and under CH600120 HMRC must either open a formal compliance check or make clear there is no obligation to send information. Read the letter closely: some ask you to act only if something is wrong, while others ask you to confirm your position or sign a certificate.
Ignoring the letter is the risky choice. HMRC now knows that you were told about the issue, and that affects how it treats any error it finds later.
Why does a nudge letter affect penalties?
A nudge letter usually turns any later correction into a prompted disclosure. HMRC’s CH82420 says a disclosure is unprompted only if you had no reason to believe HMRC had discovered, or was about to discover, the error. A letter on that exact topic gives you that reason.
The penalty ranges in CH82470 are:
| Type of error | Unprompted range | Prompted range |
|---|---|---|
| Careless | 0% to 30% | 15% to 30% |
| Deliberate | 20% to 70% | 35% to 70% |
| Deliberate and concealed | 30% to 100% | 50% to 100% |
Penalties are a percentage of the extra tax. Offshore matters can carry higher penalties, and interest runs on top; see HMRC late payment interest.
How far back can HMRC go?
HMRC’s assessing time limits for Income Tax and Capital Gains Tax, set out in CH56100, depend on behaviour:
- No careless or deliberate behaviour: 4 years from the end of the tax year
- Careless: 6 years
- Offshore matters (2015/16 onwards): 12 years
- Deliberate: 20 years
How to respond: step by step
- Check the letter is genuine. Compare it with HMRC’s list of genuine contact, and never pay or give bank details through a link in a text. See HMRC scam calls and texts.
- Note the topic and any date. Some letters set a response window or a deadline; the 2026 PSC letters, for example, use 31 January 2027.
- Compare your records with what you filed. Start with the issue the letter raises, using bank statements, P60s, dividend vouchers and rental or overseas statements.
- Correct recent years by amendment. GOV.UK says you can correct a return within 12 months of the Self Assessment deadline, so 2024/25 can usually be amended until 31 January 2027.
- Disclose older years. Use HMRC’s digital disclosure service for UK income, or the Worldwide Disclosure Facility for offshore issues. After notifying, you have 90 days to submit and pay.
- Keep a file note. If nothing is wrong, record what you checked and when. Reply if the letter asks you to.
Which applies to you?
- If your returns are correct, you need not act unless the letter asks for a reply, but keep your note of the check.
- If you made a careless error in 2024/25, amend the return online by 31 January 2027.
- If the error is in 2023/24 or earlier, use the digital disclosure service.
- If it involves overseas income, gains or assets, use the Worldwide Disclosure Facility.
- If the error may be deliberate, take advice from a tax adviser before you contact HMRC.
What advisers should do
Ask clients to forward any HMRC letter, because many go to the taxpayer only, and share information with HMRC only with the client’s permission. Assess behaviour carefully: it sets both the penalty range and how many years must be corrected. Our guide to HMRC compliance checks covers what happens if HMRC escalates.
Frequently asked questions
Is an HMRC nudge letter an investigation?
No. HMRC’s Compliance Handbook says a One to Many letter is not a compliance check. HMRC can still open a formal check later if it believes something is wrong.
What happens if I ignore a nudge letter?
Nothing happens automatically, but HMRC knows you were told. If it later finds an error on that topic, your disclosure will be treated as prompted and the minimum penalty will be higher.
What is the penalty if I find a careless error after a nudge letter?
A prompted careless error carries a penalty of 15% to 30% of the extra tax, against 0% to 30% if unprompted.
Can I amend my tax return after receiving a nudge letter?
Yes. You can amend a return within 12 months of the filing deadline, and use HMRC’s digital disclosure service for older years.
How do I know a nudge letter is genuine?
Check the topic against HMRC’s list of genuine contact on GOV.UK, and call HMRC on its published numbers, not one given in a text.
Sources
Rates, thresholds and rules in this guide were checked against HMRC and GOV.UK guidance on 6 November 2026. Tax rules change, so check the current position on GOV.UK or with a qualified adviser before acting. This guide is general information, not personal advice.
- CH600110: The One to Many approach, overview (HMRC Compliance Handbook)
- Check genuine HMRC contact that uses more than one method (HMRC)
- CH82470: Penalty ranges for inaccuracies (HMRC Compliance Handbook)
- Corrections to your Self Assessment tax return (GOV.UK)
- Tell HMRC about underpaid tax from previous years (HMRC)
- Worldwide Disclosure Facility: make a disclosure (HMRC)