HMRC Tax Investigation Guide: What to Do If HMRC Contacts You

If you have just opened a brown envelope from HMRC, you are probably feeling a knot in your stomach. That is completely normal. HMRC compliance checks — commonly called tax investigations — are intimidating by design, and the language in an HMRC enquiry letter can feel accusatory even when the enquiry is routine.

This guide walks you through every stage of an HMRC tax investigation, from the moment the letter arrives to the final settlement. It covers the types of enquiry, why you may have been selected, what HMRC can request, how long the process takes, your rights, the risks involved, and — most importantly — when you need to stop reading and get a specialist on your side.

This is not legal advice. It is a map of the process so you know what to expect and can make informed decisions at every turn.

Types of HMRC Enquiry

Not all HMRC compliance checks are the same. The scope and intensity vary dramatically depending on what HMRC is looking at:

Aspect Enquiry

This is the most common and least intrusive type. HMRC writes to ask about a specific item on your tax return — a large expense claim, a capital gain, a rental income figure, or a dividend voucher that does not match their records. They will ask for supporting evidence for that specific item. If you provide satisfactory proof, the enquiry closes. Aspect enquiries typically resolve in 3-6 months.

Full Enquiry

Here HMRC reviews your entire tax return (and possibly returns from prior years). They will request bank statements, invoices, contracts, and other records for a full review of your income and expenses. A full enquiry is more resource-intensive and usually takes 6-12 months. It may begin as an aspect enquiry and expand if HMRC finds discrepancies.

Code of Practice 9 (COP9) — Civil Investigation of Fraud

If HMRC suspects deliberate tax evasion or fraud, they may open a COP9 investigation under the Contractual Disclosure Facility (CDF). This is the most serious type of civil investigation. HMRC will invite you to confirm whether you have committed tax fraud. If you accept, you must make a full, accurate disclosure of all tax irregularities across all taxes and years. If you decline, HMRC can pursue a criminal investigation. If you receive a COP9 letter, you must instruct a specialist tax solicitor or accountant immediately. Do not respond on your own.

Random Compliance Check

HMRC also conducts random checks on self-assessment returns, VAT returns, and PAYE records. Being selected does not imply wrongdoing — you may simply be part of a statistical sample. However, it is still essential to take the process seriously and respond within the deadline.

Why Has HMRC Selected You?

There are several common triggers that increase the likelihood of an HMRC enquiry:

• High or fluctuating income — contractors, freelancers, and business owners with variable income from year to year attract attention because the variance may signal unreported income or errors.
• Large expense claims relative to income — if your expenses are disproportionate to your earnings, HMRC may question whether they are wholly and exclusively for business purposes.
• Industry risk profiling — HMRC uses computer models to flag sectors with historically higher non-compliance. Construction, property, and financial services are common targets, as are contractors operating through limited companies.
• Third-party data matching — HMRC receives data from banks, property portals, investment platforms, and gig economy operators. If your declared income does not match the data they hold (e.g., bank interest, property sales, dividends), it triggers a check.
• Related-party transactions — if you have a close company and have made loans to shareholders, or if you have transacted with a connected party at non-arm's-length values, HMRC will want to see the details.
• Random selection — as noted above, some enquiries are purely random.

None of these triggers mean you have done something wrong. They simply mean your return has been flagged for review. Many enquiries close with no adjustments.

The HMRC Investigation Process: Step by Step

1. The Opening Letter

HMRC sends a formal letter (or a "notice of enquiry" under Schedule 1A TMA 1970). The letter will specify the tax year(s) under review, the scope (aspect or full), and a deadline by which you must respond. It will also name the HMRC officer assigned to your case. Read the letter carefully to understand exactly what HMRC is asking for. The deadline is typically 30 days, but extensions are available if you request them.

2. Gather Your Records

Start collecting the documents HMRC has requested. For a contractor, this typically includes bank statements, sales invoices, purchase receipts, mileage logs, dividend vouchers, payroll records, pension contribution evidence, and contracts with clients. Do not destroy or alter any documents — doing so can be treated as a criminal offence. Your tax adviser will review the list and ensure you provide only what is relevant and proportionate.

3. Engage a Tax Adviser

Before responding to HMRC in writing or over the phone, instruct a qualified tax adviser. This is the single most important step. A good adviser will take over all correspondence with HMRC, frame your responses to minimise risk, identify any weaknesses in your position, and negotiate on your behalf. Most contractor accountants offer HMRC enquiry cover as standard. If you do not have this, a specialist tax investigation accountant or tax solicitor is your next best option.

4. Initial Response and Information Provision

Your adviser will write to HMRC acknowledging the enquiry and either providing the requested information or requesting clarification. Never withhold information HMRC is entitled to — this can aggravate penalties — but equally, do not volunteer information beyond the scope of the enquiry. Your adviser will navigate this boundary.

5. Meetings and Interviews

HMRC may request a meeting or telephone interview. You have the right to have your adviser present at any meeting. Do not attend an HMRC interview without your adviser. Even casual-sounding "fact-finding" conversations can be used as evidence. The HMRC officer will take notes that can later be used to support their conclusions.

6. HMRC's Findings

At the conclusion of the enquiry, HMRC will issue a "closure notice" setting out their findings. This will state whether they are satisfied with your return or whether they propose amendments. The closure notice will also set out any additional tax, interest, and penalties they believe you owe.

7. Appeal or Settlement

You have the right to appeal HMRC's findings to the First-tier Tribunal (Tax). Your adviser will help you decide whether to accept HMRC's conclusion, negotiate a settlement, or appeal. Most cases settle before reaching the tribunal, but having the right to appeal gives you leverage in settlement negotiations.

What HMRC Can Request

HMRC has broad information-gathering powers under Schedule 36 of the Finance Act 2008. They can issue an information notice requiring you to produce documents or provide information that is "reasonably required" for the enquiry. They can also issue a third-party notice to your bank, clients, or suppliers to request records directly. If you fail to comply with an information notice, HMRC can apply to the tribunal for a penalty or, in serious cases, a forced-entry warrant.

Common requests include:

• Personal and business bank statements
• Invoices and sales records
• Receipts for claimed expenses
• Contracts with clients and agencies
• Timesheets and work records
• Dividend vouchers and board minutes
• Payroll records (RTI submissions)
• Pension contribution certificates
• Mileage logs and travel records
• Mortgage or loan application records (HMRC cross-references declared income with borrowing capacity)
• Emails relating to specific transactions

Timeline: How Long Does an HMRC Investigation Take?

The duration depends on complexity, responsiveness, and whether HMRC finds issues:

• Aspect enquiry: 3-6 months if simple and you respond promptly.
• Full enquiry (straightforward): 6-12 months.
• Full enquiry (complex, multiple years): 12-18 months or longer.
• COP9 fraud investigation: 18-24 months is not unusual, especially if the disclosure is complex.

The fastest way through an investigation is to cooperate fully, provide complete information promptly, and let your adviser manage the process. Delaying, hiding documents, or being evasive will extend the timeline and increase penalties.

Your Rights During an HMRC Investigation

• Right to professional representation — you can appoint any tax adviser to act on your behalf. HMRC must deal with them, not you directly.
• Right to a reasonable timeframe — HMRC must give you at least 30 days to respond to information requests (though shorter deadlines can apply if there is a risk of asset dissipation).
• Right to challenge the scope — you can challenge an information notice if it is too broad or disproportionate. Your adviser can make representations to HMRC or appeal to the tribunal.
• Right to appeal — you can appeal any amendment HMRC makes to your return within 30 days of the closure notice. If the appeal is unsuccessful at HMRC review, you can take it to the First-tier Tribunal.
• Right to privilege — legal professional privilege protects communications with your solicitor. It does not automatically extend to communications with accountants, though litigation privilege may apply in some circumstances.

What Are the Risks?

The consequences of an adverse HMRC finding depend on the nature of the error and whether HMRC believes it was careless or deliberate:

• Additional tax: you will owe the tax HMRC believes you underpaid, plus interest from the original due date. Interest is currently 7.5% (late payment interest rate effective from 6 April 2026).
• Penalties for careless inaccuracy: 0-30% of the additional tax depending on the quality of your disclosure.
• Penalties for deliberate inaccuracy: 20-70% of the additional tax, or up to 100% if deliberate and concealed.
• Penalties for failure to notify: up to 100% of the additional tax for deliberate non-notification.
• Criminal prosecution: rare but possible for deliberate fraud and evasion (tax evasion is a criminal offence under the Fraud Act 2006 and the Criminal Finances Act 2017).
• Naming and shaming: HMRC can publish details of deliberate tax defaulters, which can damage your professional reputation.

The good news is that prompt, full cooperation and a skilled adviser can significantly reduce penalties. HMRC's penalty regime is designed to reward disclosure and penalise concealment.

When to Hire a Specialist Tax Adviser

You should engage a specialist tax investigation adviser in the following situations:

• Immediately after receiving an HMRC compliance check letter — before you respond or provide any information.
• If you receive a COP9 letter — this requires immediate specialist legal advice. Do not pass Go, do not collect £200.
• If the enquiry is a full enquiry — especially if it covers multiple tax years or involves complex areas like IR35, capital gains, or cross-border transactions.
• If you have concerns about your past filings — even if HMRC has not yet contacted you, if you suspect there are errors or omissions in past returns, a specialist can help you make a voluntary disclosure (which attracts lower penalties than waiting for HMRC to find the issue).
• If HMRC requests a meeting or interview — never attend without representation.
• If you operate through a limited company — contractor tax investigations are a specialism that general accountants may not handle effectively.

Contractor-Specific HMRC Investigation Risks

Contractors face specific risks that permanent employees do not. If you operate through a limited company, HMRC may investigate not just your personal tax return but also your company's corporation tax returns, VAT returns, and payroll (RTI) records. The key areas HMRC focuses on for contractors are:

• IR35 status — if HMRC believes you should have been inside IR35, they will assess back taxes on your contract income, including employee and employer NI. Read our complete IR35 guide and our dedicated HMRC tax investigation page for contractors for more detail.
• Personal versus business expenses — contractors often blur the line between business and personal expenditure. HMRC scrutinises travel, subsistence, home office, and entertainment claims particularly closely.
• Dividend planning — HMRC checks that dividends are properly documented with board minutes and that they do not exceed available distributable profits.
• VAT partial exemption — if your company is VAT-registered and you claim input VAT on mixed-use items (like a car or phone), HMRC may review your partial exemption method.

For more detail on the contractor-specific risks and how to prepare, see our HMRC tax investigation section.

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