How Do I Know If HMRC Are Investigating Me? (7 Warning Signs in 2026)
Suspecting that HMRC are investigating you is quite the ordeal, particularly when no letter has arrived, and you have no way to confirm it. HMRC rarely announces an investigation at the outset. In many cases, the first formal notification arrives only after months of quiet data-gathering, cross-referencing tax returns, and contacting third parties you may never hear about. By the time correspondence lands on your doormat, the process is already well underway.
This guide answers the question of 'how do I know if HMRC are investigating me?' by setting out the seven warning signs to look for. It explains what each type of letter means and tells you exactly what to do the moment you spot any of them.
The 7 Warning Signs HMRC Are Investigating You
1. A Compliance Check Letter
A compliance check letter is the most common opening move in a civil HMRC enquiry. Issued under Section 9A of the Taxes Management Act 1970, it notifies you that HMRC intend to examine one or more aspects of your tax return. The letter will specify whether they are conducting a full enquiry (your entire return) or an aspect enquiry (a targeted area such as expenses, rental income, or a specific transaction).
Do not assume this is routine. Even a narrow aspect enquiry can broaden if HMRC identifies additional discrepancies once they are in.
2. A COP8 or COP9 Letter
A COP8 or COP9 letter signals a significantly more serious level of scrutiny.
A COP8 (Code of Practice 8) letter is issued where HMRC suspect a complex tax avoidance arrangement but do not yet allege fraud. It is typically sent to individuals or businesses that have used aggressive tax planning schemes. HMRC's Fraud Investigation Service handles these cases rather than standard compliance teams.
A COP9 (Code of Practice 9) letter, also referred to as HMRC Code 9, indicates that HMRC formally suspects serious tax fraud. This letter introduces the Contractual Disclosure Facility (CDF) and gives you 60 days to admit the fraud or deny it in full. The distinction matters enormously: making an admission opens the CDF, which typically leads to a civil resolution rather than prosecution, while denial moves the investigation onto a criminal track.
If you have received a COP9 letter, it might be a telltale sign that simplifies the answer to how do I know if HMRC are investigating me. Instruct a specialist tax fraud solicitor before the 60-day window closes.
3. A Nudge Letter
Nudge letters are lower in severity but should never be ignored. HMRC issue them in bulk to taxpayers whose data, obtained through the Common Reporting Standard, offshore account disclosures, or the Let Property Campaign, suggest undeclared income. The letter does not confirm an investigation; it nudges the recipient toward voluntary disclosure before formal action begins. Responding appropriately and with legal advice is almost always the preferable path.
4. Sudden Information Requests to Your Bank or Agent
You may not hear from HMRC directly at all. Under powers granted by Schedule 36 of the Finance Act 2008, HMRC can issue third-party information notices to banks, accountants, solicitors, and other financial institutions, often without your prior knowledge. The first indication that HMRC are looking into your affairs may be a call from your bank or accountant confirming they have been asked to supply records.
This is a serious sign. By this stage, HMRC already has grounds to seek a tribunal-approved information notice.
5. Contact With Your Business Partners or Associates
HMRC may approach business partners, suppliers, or even employees to gather information about your financial arrangements. If a colleague mentions being contacted by HMRC in connection with your business, this is a strong indicator that an enquiry into your affairs is already live. Do not attempt to contact any of those individuals about what they have said; doing so may be interpreted as interference with the investigation.
6. A Dawn Raid
A dawn raid, formally a search and seizure operation, is authorised by a magistrates' court warrant and typically deployed where HMRC suspect serious or organised fraud. Officers from the Fraud Investigation Service will attend your home or business premises, seize documents, computers, and devices, and may question those present.
If HMRC officers arrive unannounced at your door, you have the right to legal representation before answering substantive questions. Call a solicitor immediately.
7. A Criminal Investigation Notification
If HMRC conclude that civil procedures are insufficient, they will notify you formally that a criminal investigation has begun. This notification most commonly accompanies a request to attend a voluntary interview under caution, or it is delivered at the point of arrest. Being invited to a voluntary interview under caution is not legally compulsory, but what you say can and will be used in evidence. Specialist representation at this stage is essential, not advisable.
The HMRC Investigation Letter: What It Looks Like and What Each Code Means
HMRC investigation letters arrive by post on official HMRC-headed paper and will typically quote a reference number and the name of the caseworker handling your matter. The code printed on or referenced within the letter tells you a great deal about the seriousness of your position.
COP8: Serious tax avoidance suspected. Handled by HMRC's Fraud Investigation Service. Civil resolution is usual, but not guaranteed.
COP9: Serious tax fraud alleged. The Contractual Disclosure Facility applies. A 60-day response deadline runs from the date of the letter. This is the last formal gateway to a civil rather than criminal outcome.
Neither code constitutes a criminal charge, as both are civil investigation procedures, but COP9 in particular sits at the edge of what can tip into prosecution if handled incorrectly.
Compliance Check vs Civil Investigation vs Criminal Investigation
The COP9 Contractual Disclosure Facility and the 60-Day Deadline
The Contractual Disclosure Facility is HMRC's mechanism for resolving the most serious fraud investigations without prosecution. When a COP9 letter arrives, you have two options: accept the CDF by submitting an Outline Disclosure, which is a formal, structured admission of the fraud, within 60 days; or reject it, in which case HMRC will proceed without the protections the CDF offers and may pursue a criminal route.
Accepting the CDF does not mean admitting to a crime in the criminal-law sense. It means agreeing to co-operate fully with HMRC, disclose all irregularities, and settle the outstanding liability. In exchange, HMRC commits not to criminally investigate the matters disclosed.
The 60-day window is not extendable in most circumstances if HMRC are investigating you. If you have received a COP9 letter, the deadline begins running from the date printed on it, not the date it arrives.
What To Do (and Not Do) If You Spot the Signs
Do
- Instruct a specialist tax fraud solicitor before making any contact with HMRC, your bank, or your accountant on the matter.
- Preserve all financial records, correspondence, and digital documents in their current state.
- Note the date any letter arrived and the date printed on it, as the applicable date depends on the relevant deadline.
- Seek legal advice before attending any interview, whether described as voluntary or otherwise.
Do Not
- Contact HMRC directly without legal representation. Anything you say may be used to narrow or deepen the investigation.
- Amend tax returns in a panic. Unexplained late amendments can be treated as evidence of awareness of the original error.
- Attempt to move assets or alter financial records. This can constitute a separate criminal offence.
- Ignore correspondence. A failure to respond within the specified period carries its own consequences, including tribunal action.
How Far Back Can HMRC Investigate?
If you are asking how to know if HMRC are investigating you and how far that investigation might reach, the answer depends on the nature of the case:
4 years: Where HMRC believe there has been a genuine mistake in a tax return. This is the standard limit for most compliance checks.
6 years: Where HMRC consider the error to have been careless rather than deliberate. This applies to the majority of civil enquiries.
20 years: Where HMRC alleges deliberate fraud or concealment. In cases involving deliberate behaviour, the 20-year limit may apply, depending on the circumstances.
The practical consequence is that a COP9 investigation may require you to account for transactions spanning many years. A tax fraud solicitor can advise you on which years are genuinely at risk given the specific allegations and evidence HMRC have indicated they hold.
Frequently Asked Questions
How will I know if HMRC is investigating me?
In most cases, the first formal signal is a letter: either a Section 9A compliance check notice, a COP8 letter, or a COP9 letter. In more serious cases, you may become aware through third-party contact, such as your bank or accountant being served with an information notice, business associates being approached, or, in the most serious cases, a dawn raid. HMRC are not required to notify you that you are on their radar before they begin gathering information from other sources.
What does a COP9 letter mean?
A COP9 letter, formally a Code of Practice 9 letter, means HMRC suspect you of serious tax fraud. It introduces the Contractual Disclosure Facility, which gives you 60 days to submit a formal admission (an Outline Disclosure) or reject it. Accepting the CDF and co-operating fully is almost always the preferable outcome; rejection transfers the case to a track that may lead to criminal prosecution. You should instruct a specialist solicitor before responding.
Does HMRC tell you when an investigation starts?
Not always, and not at the beginning. HMRC may gather information from banks, agents, and third parties for a considerable period before issuing any formal notification. Once a formal enquiry opens, they are required to notify you, but by that point, the groundwork of the investigation is often complete.
How far back can HMRC investigate?
Up to four years for genuine mistakes; up to six years for careless errors; up to 20 years where deliberate fraud is alleged. Where deliberate behaviour is alleged, the 20-year limit may apply, depending on the circumstances.
What triggers an HMRC investigation?
Common triggers include inconsistencies or omissions in tax returns, financial figures that are significantly out of line with industry norms, large or unexplained transactions, late or missing return submissions, undeclared offshore income identified through international data-sharing agreements, and sector-wide compliance campaigns. HMRC also conducts a proportion of investigations by random selection.
Should I speak to HMRC without a solicitor?
No. Whether you have received a compliance check letter, a COP9 notice, or an invitation to a voluntary interview under caution, speaking to HMRC without legal representation significantly increases the risk of inadvertently providing information that deepens the investigation or narrows your options. A tax fraud solicitor can engage with HMRC on your behalf, manage all correspondence, and ensure your position is protected at every stage.
Speak to a Tax Fraud Solicitor at Holborn Adams
Do you want some clarity regarding whether HMRC is investigating you or an HMRC compliance check? If you have spotted any of the signs above, or if you have already received correspondence, do not wait. The earlier you instruct specialist representation, the more options remain available.
Holborn Adams handles HMRC tax fraud investigations across the UK on a case-specific basis, and its solicitors are available 24 hours a day. Call us now or send an email to arrange a confidential, no-obligation discussion with a member of the team.
