Key Takeaways
- HMRC tax investigations range from routine compliance checks to formal enquiries. Code of Practice 9 (COP9) applies where HMRC suspects deliberate tax fraud.
- Inconsistent returns, undeclared income, VAT irregularities, offshore connections, cryptoasset transactions and tax avoidance schemes commonly trigger HMRC scrutiny.
- Delays, incomplete evidence and unsupported explanations can increase penalties and prolong an investigation.
- HMRC normally has 12 months from filing to open an enquiry, but discovery assessments can reach back 4, 6 or 20 years depending on your behaviour.
- Verify unexpected contact independently, preserve your records and give accurate, complete responses after taking professional advice.
- Inaccuracy penalties can reach 100% of the tax lost, payable on top of the tax and interest. COP9 cases can carry higher penalties.
- Take legal advice early where HMRC alleges deliberate behaviour, issues a COP9 letter, threatens prosecution or raises a substantial assessment.
- Go Legal is rated Excellent with over 300 five-star reviews and 5/5 on Trustpilot and Google, placing our solicitors among the best-reviewed litigation lawyers in England and Wales.
HMRC Tax Investigations in 2026: Why the Way You Respond Matters
HMRC is investigating more taxpayers, with more data, than ever before. It reported £8.3 billion in compliance yield in the first quarter of 2026 to 2027 alone, and its focus on wealthy individuals, offshore assets, cryptoassets and disguised remuneration continues to grow.
A compliance check letter does not mean you have committed an offence. However, how you respond shapes the outcome. Delay, incomplete evidence or an improvised explanation can turn a narrow query into a multi-year investigation with higher penalties.
If HMRC has contacted you, verify the communication independently, preserve your records and avoid giving unsupported explanations before taking advice.
What Is an HMRC Tax Investigation and What Does a Compliance Check Letter Mean?
An HMRC tax investigation usually begins as a compliance check. HMRC describes this as a review of whether you are paying the right amount of tax at the right time and receiving the correct allowances and reliefs. HMRC explains the process in its compliance checks guidance.
A check can cover:
- Income Tax
- Corporation Tax
- VAT
- PAYE and National Insurance
- Capital Gains Tax
- Inheritance Tax
- Stamp Duty Land Tax
- Offshore income, assets and transactions
A compliance check letter does not prove that you have made an error or committed fraud. HMRC may simply want to verify a return, examine a particular transaction or investigate a risk identified through its data.
The type of contact indicates how serious the matter is:
- Routine compliance check: HMRC asks focused questions or requests specific documents.
- Formal enquiry: HMRC uses statutory powers to examine a tax return. This may concern one entry or your wider records.
- Information notice: HMRC formally requires information or documents. Failing to comply can lead to a penalty.
- Code of Practice 9 (COP9): HMRC suspects deliberate tax fraud and offers a civil investigation procedure.
- Criminal investigation: HMRC considers that a criminal charge may be necessary.
Civil investigations can result in additional tax, interest and penalties without criminal charges. HMRC’s stated policy is to deal with fraud through civil procedures wherever possible, reserving criminal investigation for serious fraud or deliberate evasion where it considers a charge necessary.
Before responding, identify the tax and period under review, the return entry or transaction in question, the documents requested, whether HMRC has referred to careless or deliberate behaviour, and the response deadline.
What Triggers HMRC Tax Investigations and Which Taxpayers Face Greater Scrutiny?
HMRC investigations commonly begin when information in a return does not match other data or looks unusual. HMRC does not usually disclose the precise risk assessment behind an enquiry, so a check does not, by itself, establish deliberate underpayment.
Common HMRC Investigation Triggers
Common risk indicators include:
- inconsistent figures between returns, accounts or schedules
- late or amended returns
- unexplained losses
- unusually large expenses
- income that appears to be undeclared
- VAT irregularities, such as a large repayment claim against low turnover
- offshore income, assets or transactions
- cryptocurrency transactions or gains
- suspected disguised remuneration
- connections with tax avoidance schemes
HMRC can obtain information from financial institutions, other government bodies, overseas tax authorities and third parties. Its data-matching now extends to crypto exchanges, offshore financial centres and real-time PAYE and VAT feeds. Passive non-disclosure of offshore income or crypto gains is increasingly likely to trigger an automated risk flag.
A mismatch does not prove wrongdoing. It does mean you must be able to explain the difference with reliable records.
HMRC’s 2026 Priorities for Wealthy, Offshore and Complex Tax Matters
HMRC’s published performance data shows the scale of its compliance work:
- compliance yield of £8.309 billion between April and June 2026
- a UK tax gap of £59.2 billion for 2024 to 2025, or 6.4% of theoretical tax liabilities
- 82 positive charging decisions and 63 prosecutions in the same quarter
These figures describe HMRC’s overall activity. They do not mean every compliance check involves suspected fraud.
Wealthy taxpayers face particular attention. In summer 2026, HMRC identified more than 200 billionaires with a UK tax footprint, using its own data, public information, third-party data and information from other countries. HMRC also established its Complex Cross-Tax and Offshore team in April 2025 to address complex wealthy and offshore non-compliance.
Proposed HMRC Enforcement Measures
Some measures remain proposals rather than current law.
The Government plans new powers to recover established lower-value tax debts through bank-account deductions. The proposed limits are up to £5,000 for individuals and £10,000 for companies. The process would generally follow around 10 contact attempts over 9 to 12 months and would not apply where the taxpayer is engaging with HMRC to manage the debt. Draft legislation is expected for consultation in summer 2027.
Proposed changes to the Promoters of Tax Avoidance Schemes regime would bring VAT and other indirect taxes within the regime, broaden stop notices and allow earlier publication of promoters’ names.
What Happens During an HMRC Tax Investigation?
An HMRC investigation usually moves through initial contact, evidence gathering, HMRC’s review, discussions and a decision. HMRC may contact you by letter, telephone or through its digital services. A formal enquiry notice should identify the taxpayer, the tax return or period under review and the information required.
Practical Steps After Receiving HMRC Contact
- Verify the contact. Check unexpected communications independently through GOV.UK. Never give security information to an unverified caller.
- Identify the scope. Establish which tax, period, return entry and transaction HMRC is reviewing.
- Preserve records. Keep emails, invoices, bank statements, contracts, accounting data and digital records.
- Consider representation. Decide whether an accountant, tax adviser or solicitor should deal with HMRC.
- Review the facts. Check the records before giving explanations or making admissions.
- Respond accurately. Answer the questions asked and keep a record of every communication.
- Assess the outcome. If HMRC proposes additional tax or penalties, consider settlement, a review, alternative dispute resolution or an appeal.
At the end of the check, HMRC may find no error, repay overpaid tax with interest, or seek underpaid tax with interest and a penalty.
There is no universal deadline for completing an enquiry. Straightforward checks may conclude quickly. Investigations involving companies, several years, offshore records, connected parties or incomplete accounts can take substantially longer.
What Documents Can HMRC Request?
HMRC may request:
- accounting records and management accounts
- invoices, receipts and purchase records
- contracts and business correspondence
- payroll and PAYE records
- bank statements
- emails and other digital records
- evidence supporting deductions, losses or relief claims
Take informal requests seriously. If you do not provide the information, HMRC may issue a formal information notice, with a penalty for non-compliance.
HMRC may visit your home, business or adviser’s office, or ask you to attend an HMRC meeting. You can have an accountant or legal adviser present. You can authorise a tax agent to act for you; to use someone other than a tax agent, write to HMRC to authorise them.
How Long Does HMRC Have to Open an Enquiry?
HMRC normally has 12 months from the filing date to open an enquiry into a tax return:
- individuals: section 9A of the Taxes Management Act 1970
- partnerships: section 12AC of the Taxes Management Act 1970
- companies: Schedule 18, paragraph 24 of the Finance Act 1998
An enquiry opened outside the relevant window is normally invalid. However, if HMRC discovers a loss of tax after the window closes, it may still issue a discovery assessment. The period depends on your conduct:
- up to 4 years for an innocent error
- up to 6 years for careless behaviour
- up to 20 years for deliberate behaviour
The behaviour classification is therefore critical to limiting exposure. A finding of carelessness adds years to the period under review. A finding of deliberate behaviour can open up two decades of returns.
How Are HMRC Tax Investigation Penalties, Interest and Settlement Terms Decided?
HMRC sets penalties by reference to your behaviour, the tax lost and the quality of your disclosure. Penalties are charged on top of the tax owed and interest.
HMRC Penalty Categories and Ranges
Schedule 24 to the Finance Act 2007 classifies inaccuracies as careless, deliberate but not concealed, or deliberate and concealed. The standard penalties are 30%, 70% and 100% of the potential lost revenue respectively, before reductions for disclosure. The resulting ranges are:
| Behaviour | Unprompted disclosure | Prompted disclosure |
|---|---|---|
| Careless | 0% to 30% | 15% to 30% |
| Deliberate but not concealed | 20% to 70% | 35% to 70% |
| Deliberate and concealed | 30% to 100% | 50% to 100% |
Careless behaviour means failing to take reasonable care. Deliberate behaviour means knowingly submitting an incorrect position. Deliberate and concealed behaviour involves additional steps to hide the inaccuracy.
How Disclosure and Cooperation Affect the Penalty
A disclosure is unprompted when you tell HMRC about the error before it has reason to suspect it. It is prompted when HMRC has already identified or challenged the issue.
Where the penalty lands within the range depends on the quality of your disclosure: telling HMRC what happened, explaining how the error occurred, quantifying the tax lost, providing records and helping HMRC establish the correct position. HMRC confirms that greater assistance generally leads to a lower penalty.
Interest is charged separately from any penalty. HMRC’s late-payment and repayment interest rates increased on 6 November 2026 following a Bank of England base-rate change, so delay in settling a liability now costs more.
Since April 2026, HMRC has operated a mandatory referral process for complex penalty cases and a specialist penalty network. Cases involving multiple taxes, offshore elements or high values are reviewed by specialist penalty teams. Early, high-quality disclosure and technical arguments on behaviour classification are now even more important to securing a penalty at the lower end of the range.
What Happens Under Code of Practice 9?
A COP9 letter means HMRC suspects deliberate tax fraud. It should never be treated as an ordinary compliance check.
Under COP9, HMRC offers you the opportunity to make a complete disclosure under a formal contract. In return, HMRC will not pursue criminal prosecution, provided the disclosure is full and accurate.
The risks include:
- substantial tax, interest and penalties
- penalties that, according to HMRC’s COP9 guidance, can be unlimited and in some cases exceed 200% of the tax or duty lost, subject to reduction depending on the quality of disclosure
- publication as a deliberate defaulter
- criminal prosecution if the disclosure is incomplete or inaccurate
Do not respond to a COP9 letter with a broad admission or denial before reviewing the accounting records, contracts, ownership structure and advice you relied on. Our solicitors can manage the disclosure process, advise on civil fraud risk and protect legally privileged communications. If you have received a COP9 letter, book a free consultation before you reply.
What Are Your Rights During an HMRC Investigation?
You can authorise an accountant or solicitor to deal with HMRC on your behalf, and you can ask for more time where you have a valid reason.
If HMRC issues an appealable decision, you will usually have 30 days to:
- provide further information
- request an internal review by another HMRC officer
- appeal to the First-tier Tribunal (Tax)
The right route depends on the decision and the strength of your evidence. A review may suit a case where HMRC has misunderstood the facts or calculations. Alternative dispute resolution may help where discussions have stalled. A tribunal appeal should identify the exact decision under challenge, the relevant facts and documents, the legal basis of the challenge and the outcome you want.
Our solicitors advise on First-tier Tribunal (Tax) appeals. Because the 30-day window is short, take advice as soon as an assessment or penalty notice arrives.
Common Mistakes That Escalate HMRC Investigations
- Delayed responses. Missed deadlines invite information notices and damage the cooperation credit that reduces penalties.
- Incomplete disclosure. Disclosing part of a problem and leaving HMRC to find the rest undermines the quality of disclosure across the whole case.
- Unsupported explanations. An account that the documents later contradict can push HMRC towards a deliberate-behaviour finding.
- Late professional advice. Positions taken in early correspondence are hard to reverse.
- An adversarial tone without legal basis. Challenging HMRC is legitimate where the law supports you; obstruction without grounds rarely helps.
When Should You Instruct a Solicitor for an HMRC Investigation?
Legal advice is particularly important where:
- HMRC is examining several tax years
- the investigation involves complex transactions or connected entities
- HMRC alleges careless or deliberate behaviour
- you receive a COP9 letter
- criminal investigation is threatened
- the assessment or penalties are substantial
- you need to challenge an assessment or appeal to the Tax Tribunal
Many accountants handle straightforward compliance checks effectively. A solicitor adds value where the matter turns on legal privilege, procedural arguments, disputed behaviour classifications, settlement negotiations or tribunal proceedings.
Our tax-dispute solicitors represent individuals, directors and businesses in HMRC enquiries, penalty negotiations, COP9 matters, settlement discussions and appeals. We handle Income Tax, Corporation Tax, VAT, PAYE, National Insurance, Capital Gains Tax, Inheritance Tax, Stamp Duty Land Tax, offshore disclosure, disguised remuneration and IR35 disputes.
Tax investigations often overlap with other disputes. Where HMRC’s findings expose disagreements between company officers, our team also advises on director and shareholder disputes. If poor tax advice caused the underpayment, we can advise on professional negligence claims against tax advisers.
Frequently Asked Questions About HMRC Tax Investigations
Get Expert Help With Your HMRC Tax Investigation
The early stages of an HMRC investigation often decide its outcome. The behaviour classification HMRC settles on determines both the penalty range and how many years it can reopen, and the 30-day window to challenge a decision closes quickly. Acting promptly matters most where you face a COP9 letter, a complex penalty referral, a substantial assessment or an appeal deadline.
Our tax-dispute solicitors advise individuals, directors and businesses across England and Wales on HMRC enquiries, disclosures, penalty negotiations, settlement discussions and Tax Tribunal appeals. We will assess HMRC’s contact, protect your position and help you respond with accurate evidence and properly reasoned representations. Call us on 0207 459 4037 or book a free consultation with our team.
