If a brown envelope arrives from HMRC with a subject line like "Your tax position may be incorrect" or "Information we have suggests…", you have received a nudge letter. These are not formal enquiries — but they are not friendly chit-chat either. They are HMRC's way of inviting you to disclose and correct an issue before the agency opens a formal investigation. The way you respond, and the speed at which you respond, materially affects what happens next.
What a nudge letter is
Nudge letters are part of HMRC's "promote, prevent, respond" strategy. The agency uses third-party data to identify taxpayers it believes may have under-declared or made an error, and writes to them rather than opening an immediate enquiry. Common nudge letter campaigns in the last 18 months:
- Cryptoasset holders: identified from exchange data and CARF predecessors.
- Overseas income: identified through the Common Reporting Standard.
- Property landlords: identified through tenancy deposit schemes, agents, and Land Registry data.
- Online sellers on eBay, Etsy, Amazon, Vinted, Depop and similar platforms.
- Short-term lets: identified through Airbnb data.
- Persons of significant control whose declared income does not match their corporate position.
- Recipients of large transfers from offshore.
What a nudge letter is not
A nudge letter is not a Section 9A enquiry. HMRC has not opened a formal investigation. There is no statutory deadline by which you must respond, and (technically) no legal obligation to reply at all. Some practitioners have advised silence as a strategy.
That advice is, in our view, almost always wrong. Ignoring a nudge letter increases the probability that HMRC will open a formal enquiry on its own information, with the worst penalty bands applicable because the disclosure is treated as prompted rather than unprompted.
The three response options
- Confirm your tax position is correct. If you have reviewed your records and there is no under-declaration, write back and say so. Provide enough information to satisfy the case officer (which depends on the campaign) and keep a copy.
- Make a disclosure via the appropriate facility. If there is an error, the right route is usually the Digital Disclosure Service (for most under-declarations), the Worldwide Disclosure Facility (offshore), or the Let Property Campaign (residential lettings). Disclosing yields the lowest penalty bands.
- Engage and seek time. If you need to reconstruct records, write back to say so and request a reasonable extension. HMRC will usually grant 30 to 60 days.
Why the penalty difference matters
Penalties for inaccuracies are a percentage of the unpaid tax. The bands differ significantly between prompted and unprompted disclosure:
- Unprompted disclosure of careless behaviour: 0% to 30%, with maximum mitigation reducing to 0%.
- Prompted disclosure of careless behaviour: 15% to 30%, minimum 15%.
- Unprompted disclosure of deliberate behaviour: 20% to 70%, mitigation to 20%.
- Prompted disclosure of deliberate behaviour: 35% to 70%, minimum 35%.
A nudge letter response counts as unprompted if you respond before HMRC has confirmed an enquiry has begun. That is the strategic opportunity the nudge letter creates — and the reason you should not let it pass.
Common mistakes when responding
- Treating it as a "tickbox" reply. Generic responses without supporting evidence get escalated.
- Volunteering more than necessary. A nudge letter on overseas income should be answered with offshore information, not a complete review of your domestic affairs.
- Missing related issues. If the nudge is about property income and you also have unreported crypto, dealing with one and not the other is asking for a second letter — and the second letter will not be a nudge.
- Trying to draft the letter without specialist input. The language matters. We have seen taxpayers admit to "deliberate" behaviour in casual phrasing that triggered the worst penalty band.
A typical timeline
- Day 0: letter received. Take the envelope to your accountant.
- Days 1 to 5: triage. What information does HMRC have? What is the underlying issue? Is there an under-declaration?
- Days 5 to 20: records reconstruction or confirmation. Identify the right disclosure route if needed.
- Days 20 to 30: response drafted. If a disclosure is needed, file via the Digital Disclosure Service or relevant facility.
- Days 30 to 60: HMRC acknowledgement and any follow-up.
The right specialist support transforms the outcome. Our team has handled hundreds of nudge letter responses and we have a clear framework for each campaign type. To get started, book a confidential 20-minute call, or write via the contact page attaching a scanned copy of your letter. We will reply with an initial view within one working day and can then work alongside your existing Self Assessment position to manage the disclosure cleanly.