An HMRC nudge letter is not a tax investigation — but it means HMRC already has data that suggests you may have underpaid tax. Ignoring it puts you in a much worse position if HMRC follows up. Here is exactly what a nudge letter means, what to do about it, and how to respond correctly in 2026/27.
What Is a Nudge Letter?
HMRC’s nudge letter programme (officially called “one-to-many” communications) sends automated letters to taxpayers whose data — obtained from third-party sources — appears inconsistent with their declared income.
Unlike a formal enquiry, a nudge letter:
- Is not a statutory notice under TMA 1970 s9A
- Does not impose a legal obligation to respond
- Does not open a formal investigation
- Is not a finding that you have done anything wrong
What it is: a signal that HMRC’s data suggests something may be missing — and an invitation to put it right before HMRC looks harder.
Common Nudge Letter Types
| Topic | What triggered it |
|---|---|
| Online selling income | Platform data (eBay, Vinted, Etsy) under DAC7 reporting rules |
| Rental income | Land Registry data, letting agent reports, tenant references |
| Cryptocurrency gains | Exchange data, blockchain analytics |
| Capital gains | Share dealing platform data, Companies House |
| Overseas income or assets | International tax authority data exchange (CRS/FATCA) |
| Self-employment income | Bank data, Companies House, online marketplace data |
| Dividend income | Company filings, investment platform reports |
What to Do When You Receive a Nudge Letter
Step 1: Read it carefully
Note exactly what income or activity HMRC is asking about. The letter will typically reference a specific tax year or type of income. It will usually ask you to review your tax returns for the last 4 years and amend if needed.
Step 2: Check your tax position
Review your returns for the years mentioned. Ask yourself:
- Was all income for this activity declared?
- Were all capital gains reported?
- Was the trading allowance, property allowance, or chattel exemption applicable?
Step 3: Act — even if the answer is “nothing to declare”
If you have income to declare, amend your return or make a disclosure as soon as possible. The disclosure will be treated as prompted (because of the nudge letter) — but acting quickly limits further interest and shows cooperation, which affects penalty levels.
If you have nothing to declare, you may not need to take formal action — but document why, in case HMRC follows up.
Step 4: Consider professional advice
If the amounts involved are significant, or if you are unsure whether the income is taxable, get professional advice before responding. An accountant or tax adviser can help you assess the position correctly and, if needed, handle the disclosure on your behalf.
The Disclosure Penalty Hierarchy
| Type of disclosure | Penalty range (careless error) |
|---|---|
| Unprompted — before any HMRC contact | 0–30% |
| Prompted — after nudge letter or HMRC contact | 15–30% |
| After formal enquiry opens | 30–70% |
| Deliberate concealment | 30–100% |
| Deliberate concealment (offshore) | Up to 200% |
Cooperating with HMRC and making full disclosure always reduces penalties. The least cooperative position attracts the highest rate within each range.
Worked Example: Rachel and Her Airbnb Income
Rachel let her spare room on Airbnb for 3 years, earning around £6,000/year. She was not aware she needed to declare it — she thought it was covered by the Rent a Room scheme. She receives a nudge letter about online letting income.
Rachel reviews her position:
- Rent a Room relief: £7,500/year tax-free for letting furnished rooms in your main home
- Her £6,000/year is fully covered — she owes no tax
Rachel notes this for her own records but does not need to amend any returns. If HMRC contacts her again, she can explain her position clearly.
Compare: If Rachel had let out a second property earning £6,000/year (not covered by Rent a Room), she would need to amend her returns, declare the income, and pay the tax plus interest. The prompted disclosure would attract a penalty of around 15–30% of the unpaid tax.
How Far Back Can HMRC Look?
| Error type | HMRC look-back period |
|---|---|
| Innocent (no carelessness) | 4 years |
| Careless (reasonable care not taken) | 6 years |
| Deliberate concealment | 20 years |
A nudge letter for online income in 2026 could in theory lead HMRC to examine returns back to 2020/21 (6 years) if the error is considered careless.
Interest on Unpaid Tax
Interest runs at 7.75% per annum from the date tax was originally due. This is not a penalty — it runs regardless of the reason for underpayment. For a £2,000 underpayment over 3 years, interest adds roughly £465.
See our HMRC compliance check guide, what happens if HMRC investigates me, and selling personal belongings online tax guide.