HMRC protected £48 billion from tax fraud and non-compliance in 2024/25. A growing share of that figure came from HMRC tax letters sent directly to taxpayers, prompting them to check their affairs before a formal investigation begins. Receiving one does not mean you owe tax, and it does not mean an enquiry has started. It does mean HMRC’s data has flagged something it wants you to look at, and your reply (or silence) shapes what happens next.
Why HMRC is sending more tax letters than ever
HMRC now compares data from banks, building societies, online platforms, overseas tax authorities, and the Land Registry to identify potential discrepancies in tax returns. The system, known as Connect, cross-references billions of data points against reported income.
When a mismatch appears, HMRC does not always open a formal enquiry. Instead, it sends what is known as a “nudge letter”, asking the recipient to review their tax position and correct any errors within 30 days. This approach is far cheaper than a full compliance check and allows HMRC to contact thousands of taxpayers at once.
In 2024/25, upstream compliance activity (interventions that happen before a formal investigation) accounted for 43% of HMRC’s total compliance yield, up from 24% in 2019/20. For individuals, that means a letter through the door is now the most likely first contact you will have with HMRC about a suspected error, well before any formal enquiry is opened.
Common reasons individuals receive HMRC letters
The range of topics covered by these letters has expanded considerably in recent years. You might receive one if HMRC believes you have:
- Undeclared savings interest that exceeds your Personal Savings Allowance
- Unreported rental income from UK or overseas property
- Capital gains from selling property, shares, or crypto assets that were not included on your tax return
- Overseas income or assets flagged through the Common Reporting Standard, which now covers more than 100 jurisdictions
- Errors in a Self Assessment return, including overclaimed expenses or incorrect relief claims
HMRC also writes to taxpayers affected by specific policy changes. Recent campaigns have targeted individuals caught by the High Income Child Benefit Charge, those needing to repay Winter Fuel Payments through a tax code adjustment, and people who may have overpaid National Insurance contributions.
The difference between a nudge letter and a compliance check
Not all HMRC letters carry the same weight. A nudge letter is informal. It asks you to review your affairs and, if necessary, make a voluntary disclosure or amend a return. It is not an investigation, and receiving one does not mean HMRC has concluded you owe tax.
A compliance check letter is different. It will ask for specific information, such as bank statements, rental records, or transaction histories, and sets out a formal process. If you receive a compliance check letter, you have legal obligations around how and when you respond.
The distinction matters because the two types of letter require different responses. Treating a nudge letter as something you can ignore, or treating it as a full investigation, can both lead to problems.
What to do when you receive an HMRC Letter
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- Read it carefully and identify whether it is a nudge letter or a formal compliance check. Look for references to specific tax years, income sources, or relief claims. Genuine HMRC letters reference your Unique Taxpayer Reference or National Insurance number and direct you to GOV.UK or your Personal Tax Account.
- Resist the urge to reply on the same day. Many nudge letters include a Certificate of Tax Position, which asks you to confirm your affairs are in order. The Chartered Institute of Taxation recommends against completing this certificate without professional advice. The certificate is not restricted to a single tax year, and signing it without a thorough review could create problems later.
- Check the tax years mentioned in the letter against your bank statements, investment records, and any income sources HMRC may hold data on. Banks report savings interest directly to HMRC. Basic rate taxpayers can earn up to £1,000 in savings interest tax-free, higher rate taxpayers have an allowance of £500, and additional rate taxpayers receive no allowance at all.
- If the letter touches on overseas income, property disposals, crypto assets, or a business you own, get an accountant involved before you write back. The way the response is framed feeds directly into how HMRC categorises any underpayment and the penalty band that follows.
How to check if an HMRC letter is genuine
With HMRC moving towards digital communications from April 2026, the risk of scam letters is increasing. Fraudsters use printed letters, emails, and text messages that closely mimic official HMRC branding, often timed around key tax deadlines.
Genuine HMRC letters will:
- Include your correct UTR or National Insurance number
- Reference specific tax years or known records
- Direct you to GOV.UK or your Personal Tax Account
- Use an email address ending in @hmrc.gov.uk
Scam letters will often:
- Demand urgent payment or threaten arrest
- Ask for bank details, passwords, or copies of identification documents
- Include links to websites that are not on the GOV.UK domain
- Use premium rate phone numbers
GOV.UK publishes a regularly updated list of genuine letters currently being sent by HMRC. If you are unsure, check this list before responding. You can report suspicious correspondence by forwarding emails to phishing@hmrc.gov.uk or texting 60599.
What April 2026 means for HMRC letters
HMRC is phasing out most posted letters as part of a wider move to digital communications. From April 2026, taxpayers who use the HMRC app or a Personal Tax Account will receive digital letters instead, with an email notification alerting them to log in and read.
The aim is for 90% of HMRC interactions to be digital by the 2029/30 tax year. Taxpayers who do not use digital services can opt out and continue to receive paper letters, but the default will shift.
This change means it is more important than ever to keep your HMRC online account up to date, including your email address and contact details. Missing a digital letter carries the same consequences as missing a posted one.
When ignoring a letter becomes costly
A nudge letter is not a legal demand. There is no statutory requirement to complete the Certificate of Tax Position that often accompanies it. But ignoring the letter entirely is rarely sensible.
If HMRC later opens a formal enquiry and finds underpaid tax, your failure to act when prompted will be taken into account when calculating penalties. HMRC applies higher penalties where it considers the taxpayer’s behaviour to have been careless or deliberate, and not responding to a clear prompt can shift that assessment.
Voluntary disclosure made before HMRC escalates typically attracts a lower penalty band than a disclosure made only after an enquiry begins. Under HMRC’s current penalty regime, a careless error disclosed without prompting can attract a penalty as low as 0% of the tax due, while the same error disclosed only after HMRC prompts you can sit between 15% and 30%. A deliberate error disclosed after prompting can run from 35% up to 70%, or higher where offshore matters are involved.
Frequently asked questions
How long do I have to respond to an HMRC nudge letter?
Most nudge letters give you 30 days from the date on the letter. If you need longer to gather records or take advice, contact HMRC in writing before the deadline to explain why.
Does receiving an HMRC tax letter mean I am being investigated?
No. A nudge letter is a prompt, not an enquiry. HMRC only opens a formal investigation through a compliance check letter, which clearly references its statutory powers and asks for specific documents.
Should I sign the Certificate of Tax Position that came with my letter?
Not without advice. The certificate is open-ended and covers all your tax affairs, not just the issue raised in the letter. Most professional bodies recommend replying by letter instead.
What happens if I ignore an HMRC tax letter?
Ignoring it does not make the issue go away. If HMRC later finds an error, your failure to act when prompted will push any penalty into a higher band and may increase the chance of a formal enquiry.
Talk to Wilson Partners before you reply
If you have received a letter from HMRC and you are not sure what it means or how to respond, talk to us before you do anything. We regularly help clients review HMRC correspondence, confirm whether it is genuine, and advise on the right course of action.
Replying correctly the first time often keeps any penalty in the lowest band HMRC will apply. Contact our tax team to discuss your situation.
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