An HMRC nudge letter is a mass-issued compliance prompt telling you that HMRC’s data suggests something in your tax affairs may not add up, and inviting you to check and correct it before a formal investigation begins. It is not itself an investigation, not a legal demand, and you are not legally required to sign the form that usually comes with it. Ignoring it, though, is the worst option: HMRC already holds the underlying data, and silence is what turns a nudge into a compliance check.
Respond, review your records for the years in question, and if you find underpaid tax, disclose it through the right route within the timeframes below.
Why HMRC Sent You One
Nudge letters go out because a mismatch has already been spotted. HMRC receives automatic information on overseas bank balances, interest, and dividends from more than 100 jurisdictions under the Common Reporting Standard,1OECD. CRS by Jurisdiction and equivalent reporting on US accounts under FATCA.2U.S. Department of the Treasury. Agreement Between the Government of the United States of America and the Government of the United Kingdom to Improve International Tax Compliance and to Implement FATCA Domestically, UK banks and building societies report interest annually,3GOV.UK. Bank and Building Society Interest Returns Land Registry records property transactions, and Companies House records shareholdings and directorships. HMRC can also compel third parties to hand over records under Schedule 36 of the Finance Act 2008.4Legislation.gov.uk. Finance Act 2008 Schedule 36
All of it flows into HMRC’s Connect system, which cross-references third-party data against filed returns. If the two pictures don’t match, you get a letter.
The Most Common Triggers
The letter usually references a campaign area, though it rarely tells you precisely what HMRC thinks is wrong. Frequent triggers include:
- Offshore income and gains. Undeclared foreign interest, dividends, or capital gains showing up in CRS data but missing from Self Assessment. These cases can also fall inside the offshore penalty regime described below.
- Cryptoasset disposals. HMRC has run crypto campaigns since late 2021, with further waves in 2023 and 2024, using data obtained from exchanges. Selling, swapping, or spending crypto can produce a Capital Gains Tax liability, and the annual exempt amount is only £3,000 for 2025-26.5GOV.UK. Capital Gains Tax Rates and Allowances
- Rental income. The Let Property Campaign targets landlords who have not declared rental profits or have overclaimed expenses; HMRC matches Land Registry ownership against Self Assessment.6GOV.UK. Let Property Campaign: Your Guide to Making a Disclosure
- Capital Gains Tax on property sales. Any sale of a residential property that isn’t your main home must be reported and paid within 60 days of completion.7GOV.UK. Report and Pay Your Capital Gains Tax – If You Sold a Property in the UK
- High Income Child Benefit Charge. If you or your partner earn over £60,000 and one of you receives Child Benefit, you owe 1% of the benefit for every £200 of income above £60,000, rising to a full repayment at £80,000.8GOV.UK. High Income Child Benefit Charge
- P11D discrepancies. Where employer-reported benefits (company car, private medical, loans) don’t match what you declared.
The Certificate of Tax Position: Don’t Rush To Sign
Many nudge letters enclose a “Certificate of Tax Position.” It asks you to tick a box confirming either that your affairs are in order or that you intend to disclose, and to sign a declaration that carries a criminal-offence warning for false statements.
You are not required to sign it. HMRC has confirmed that a written response is acceptable instead. The reason to think carefully before signing is straightforward: if you tick the “everything is correct” box and HMRC later finds an error, it has a signed document that can be used to argue the error was deliberate rather than careless. That single characterisation can double or triple your penalty.
If you’re confident your affairs are correct, reply by letter and set out why. If you know a disclosure is needed, you can register for the relevant disclosure facility directly without signing the certificate.
Reviewing Your Position
Before you reply substantively, work out whether tax is actually owed. Pull together, for each relevant year: UK and overseas bank statements, records of any disposals (property, shares, crypto, including acquisition cost and exchange rates on the transaction dates), rental accounts with lease agreements and expense receipts, and copies of the Self Assessment returns you filed. Compare each year’s figures line by line against your return. Small omissions of interest or dividends are the most common finding, and they compound quickly once interest is added.
How Far Back To Look
HMRC’s assessment time limits depend on behaviour:9HM Revenue & Customs. Compliance Handbook – Assessing Time Limits
- 4 years for straightforward errors where you took reasonable care.
- 6 years where the error was careless.
- 12 years for offshore matters, under the extended limit introduced by the Finance Act 2019, regardless of whether the error was careless or deliberate.10Legislation.gov.uk. Finance Act 2019 – Time Limits for Assessments
- 20 years for deliberate behaviour.
If the letter concerns offshore income, assume 12 years and organise your figures year by year so each can be entered separately when you disclose.
What the Penalties Look Like
HMRC’s penalty regime turns on two things: how the error happened (reasonable care, careless, deliberate, deliberate and concealed) and whether you came forward before HMRC contacted you (unprompted) or afterwards (prompted). Penalties are a percentage of the tax that went unpaid — the “potential lost revenue.”
Reasonable Care Means No Penalty
If you took reasonable care and still got something wrong, no penalty applies. HMRC judges reasonable care against your circumstances: a sole trader with simple affairs isn’t held to the same standard as a director with complex international holdings.11GOV.UK. Compliance Handbook – Penalties for Inaccuracies: What Is Reasonable Care Keeping adequate records, seeking advice on unfamiliar points, and flagging uncertainty on the return itself are the core expectations. Flagging an uncertain figure and getting it wrong is treated as reasonable care rather than carelessness.
Penalty Ranges Under Schedule 24
Under Schedule 24 of the Finance Act 2007:12Legislation.gov.uk. Finance Act 2007 Schedule 24 – Penalties for Errors
- Careless, unprompted: 0% to 30%
- Careless, prompted: 15% to 30%
- Deliberate, unprompted: 20% to 70%
- Deliberate, prompted: 35% to 70%
- Deliberate and concealed, unprompted: 30% to 100%
- Deliberate and concealed, prompted: 50% to 100%
Here’s why timing matters. A nudge letter is a prompt. Any disclosure you make after receiving one falls into the prompted column, with the higher minimums. Coming forward before a letter arrives puts you in the unprompted column with lower floors, sometimes zero. If you know there’s a problem in your affairs and no letter has yet landed, that gap is worth acting on.
The Offshore “Failure To Correct” Penalty
Anyone who had undeclared offshore liabilities as of 30 September 2018 and failed to correct them by that date faces a separate penalty of 200% of the tax owed, reducible to a floor of 100% depending on the quality of disclosure.13GOV.UK. Compliance Handbook – Requirement to Correct: Failure to Correct Penalty This sits on top of the normal penalty regime and applies whether the original error was careless or deliberate. If your nudge letter concerns offshore income covering pre-2018 years, this will likely be the largest number in your calculation.
Making a Disclosure
If your review shows underpaid tax, you disclose through HMRC’s Digital Disclosure Service. There are two stages: notification and disclosure.14GOV.UK. Make a Voluntary Disclosure to HMRC
You first notify HMRC that you intend to disclose and receive a unique disclosure reference number. From the date HMRC acknowledges the notification, you have 90 days to calculate the tax, interest, and penalties, submit the completed disclosure, and pay. If you can’t pay in full, you need a payment arrangement agreed with HMRC before the 90 days expire.
If you notify and later realise you don’t need to disclose after all, phone the helpline to say so. Going silent leaves HMRC chasing you for the disclosure it’s expecting.
Offshore Issues Use the Worldwide Disclosure Facility
Where the underpaid tax relates wholly or partly to offshore income, assets, or activities, use the Worldwide Disclosure Facility instead of the standard route. The WDF runs through the same Digital Disclosure Service portal but flags the disclosure as offshore.15GOV.UK. Make a Disclosure Using the Worldwide Disclosure Facility Any onshore liabilities are included in the same WDF disclosure rather than submitted separately. The same 90-day window applies. HMRC can refuse a WDF application where it suspects criminal property, and disclosures from taxpayers already under investigation are referred to the investigating officer.
After You Submit
HMRC acknowledges the disclosure and reviews it. If accepted, the matter is closed unless new information appears later. If HMRC needs clarification, it writes with specific questions. An incomplete or inaccurate disclosure can trigger higher penalties, a formal investigation, or in serious cases publication of your details on GOV.UK.
If You Need More Time
Nudge letters typically give 30 days to respond, though some campaigns use 60. If you can’t meet the deadline, contact HMRC by phone or webchat and ask to be transferred to the extra support team. Extensions may be granted for health conditions, cognitive difficulties, financial hardship, hospitalisation, or domestic abuse, and evidence may be requested.16GOV.UK. Get Help from HMRC If You Need Extra Support
Even without special circumstances, a call to say you’re gathering records and will respond by a specific date is far better than silence. Visible engagement rarely gets escalated.
If HMRC Later Issues an Assessment
You can’t appeal the nudge letter itself. It’s an invitation to self-correct, not a decision. Appeal rights only kick in if HMRC moves beyond the nudge stage and issues a formal assessment or penalty notice. You then have 30 days from the date of that decision to appeal, stating what you disagree with, why, and what the correct figures should be with supporting calculations.17GOV.UK. Appeal a Tax Decision
The case worker who made the decision reviews it first. If you can’t agree, HMRC offers an internal review; you have 30 days to accept the review, or you can skip it and go directly to the tax tribunal. A review can also be requested later, after appealing.
What Silence Actually Costs
Ignoring the letter doesn’t remove the underlying data mismatch. The typical escalation is a formal compliance check, information notices requiring you to produce documents, and eventually an assessment raised on HMRC’s own figures. By then you’re in the prompted-disclosure column at best, with the higher penalty floors, plus late-payment interest running across every year in scope. For offshore pre-2018 failures, the Failure To Correct penalty of up to 200% of the tax owed can sit on top.
Criminal prosecution for tax fraud remains rare and is reserved for the most serious cases, but it exists as a backstop: the maximum prison sentence for the most serious offences was doubled from 7 to 14 years under provisions announced in the Spring Budget 2023, applying across taxes and duties administered by HMRC.18GOV.UK. Doubling the Maximum Prison Term for the Most Egregious Examples of Tax Fraud
The single most useful thing to do after a nudge letter arrives is respond promptly, even if the response is only that you are gathering records and will provide a full answer within a stated timeframe. Engagement keeps the file in your hands; silence hands it to a compliance officer.