What Happens if HMRC Investigates Your Business in 2026?

This article provides general information for UK small business owners and does not constitute legal, tax, or financial advice. All sources are referenced at the end of the article.

Introduction

Receiving a letter from HMRC to say your tax affairs are under review is an unsettling experience. Many business owners assume it means they have done something wrong. That is rarely the case. According to GOV.UK guidance, HMRC carries out compliance checks to make sure businesses are paying the right amount of tax, getting the right allowances and reliefs, and to discourage evasion – not simply to pursue wrongdoing. Some investigations are triggered by data discrepancies; others are entirely random. What matters is how you respond.

“Being selected for a check does not necessarily mean HMRC thinks you have done anything wrong”.

This guide explains what an HMRC investigation involves in 2026, what your rights are as a business owner, and the practical steps you should take if a letter lands on your desk. The aim is to give you an honest picture of the process so you can approach it calmly and methodically.

What Is an HMRC Investigation?

An HMRC investigation — also referred to as an enquiry or compliance check — is a formal review of your tax returns, accounts, or business records. As GOV.UK explains, HMRC has the right to check whether any tax return is accurate and complete. HMRC has legal powers to check that tax returns and business records are accurate. In most cases, you will receive written or telephone notice before HMRC requests any information.

Investigations vary considerably in scope. At one end, HMRC may ask a limited number of questions about a specific figure in your return. At the other, a full inquiry may examine several years of records across all taxes. The nature of the investigation will determine how much time, cost, and disruption is involved.

The main types of HMRC investigation

Aspect enquiry: HMRC focuses on one specific area of your tax return, such as a particular expense claim or income figure. These are usually narrower in scope and may be quicker to resolve than a full enquiry.

Full enquiry: HMRC examines the whole of your tax return. These are more involved and may require you to produce detailed records going back several years.

PAYE and employer compliance review: If you employ staff, HMRC may review your payroll, National Insurance contributions, and benefit-in-kind records separately from your business tax affairs.

VAT inspection: If your business is VAT-registered, HMRC may ask to inspect your VAT records and, in some cases, visit your business premises. The amount of notice given can depend on the type of check.

Code of Practice 8 or 9 investigations: In more serious cases, HMRC may use specialist investigation procedures known as Code of Practice 8 or 9.

Why Might HMRC Investigate Your Business?

HMRC uses data-matching tools, third-party information, and industry benchmarks to identify returns that appear inconsistent or unusual. GOV.UK guidance confirms that certain factors may prompt a compliance check, including figures that look unusual, large VAT refund claims where turnover is low, or a low declared tax liability against high turnover. Being selected does not necessarily mean HMRC suspects wrongdoing. Common factors include:

• A significant fall in reported profits compared with previous years
• Expenses that appear high relative to the type or size of your business
• Discrepancies between figures you have reported and information HMRC holds from third parties such as banks, payment processors, or Companies House
• Inconsistencies between your personal lifestyle and your business’s declared income
• Operating in a sector HMRC has identified as higher-risk for non-compliance
• Random selection, which HMRC uses to maintain compliance across the general population

HMRC uses a range of data sources and matching tools (known as Connect) to help identify inconsistencies, including information from other public bodies and third parties such as banks, the Land Registry, and the DVLA. HMRC also now receives more financial data from overseas tax authorities, and from digital platforms such as online marketplaces, under UK and international reporting rules — so income from these sources may be more visible than in the past.

What Happens When HMRC Opens an Investigation?

According to GOV.UK, HMRC will call or write to tell you what it wants to check and why. The process is broadly predictable, though the timeline and detail will vary depending on the type and complexity of the enquiry.

Stage 1: The opening letter or call

You will normally receive a formal letter from HMRC setting out the scope of the enquiry and requesting specific documents or information. HMRC may also telephone first — treat any HMRC contact professionally and keep a note of the details. Read the letter carefully. It will tell you which tax year or years are under review, which taxes are being examined, and what HMRC is asking for. Note any deadlines.

You can ask HMRC to clarify what they are looking for if the letter is unclear. GOV.UK confirms that if you need more time, HMRC may agree to an extension where there is a valid reason — write to HMRC to request this before the deadline passes.

Stage 2: Gathering your records

HMRC will typically ask for business records such as bank statements, invoices, receipts, payroll records, and VAT records. The documents requested will depend on the type of investigation.

If your records are incomplete, do not attempt to reconstruct them dishonestly. If genuine gaps exist, disclose this to HMRC and explain the reasons. Being open at this stage generally helps reduce the risk of penalties.

Stage 3: Correspondence and negotiation

In many cases, an HMRC enquiry involves a series of written exchanges rather than face-to-face meetings. HMRC will ask questions; you or your adviser will respond. This process can take several months, sometimes longer for complex cases.

You can usually appoint an accountant or other authorised adviser to deal with HMRC on your behalf, subject to formal authorisation. If you are not represented, consider seeking professional advice before responding, particularly if the sums involved are significant.

Stage 4: Resolution

Many enquiries end with HMRC accepting the taxpayer’s explanation or with an agreed adjustment to the figures. If additional tax is due, you will normally have the opportunity to discuss the figures before a formal settlement is reached.

Where HMRC considers errors to have been deliberate, penalties may be applied on top of the tax owed. Penalties are generally calculated as a percentage of the unpaid tax and depend on behaviour and the level of disclosure. Making a voluntary and full disclosure generally helps reduce the level of penalty applied.

Stage 5: Appeals

If you disagree with HMRC’s conclusions, you can appeal. According to GOV.UK, you should write to HMRC to explain why you think a decision should change. This normally goes through HMRC’s own internal review process first, before you can take the matter to the First-tier Tribunal, which is an independent body. You do not need a lawyer to appear at the Tribunal, though professional representation is common for significant cases.

A Practical Example

Consider a sole trader running a small consultancy. In 2024/25 her profits fell compared with the previous year, and her bank statements showed several large personal deposits that were in fact repayments of a personal loan from a friend, rather than business income. This kind of discrepancy is the sort of thing that can prompt an aspect enquiry.

Because she had clear documentation showing the source of those deposits — a signed loan agreement and bank statements from her friend — she was able to respond fully within a few weeks. HMRC accepted her explanation and closed the enquiry without requiring any additional tax. Her accountancy fees for handling the enquiry came to a few hundred pounds.

Had she not kept that documentation, she would have needed to explain the deposits using whatever other evidence she could provide. The outcome might have been the same, but the process would likely have taken longer and felt more stressful.

What Will an HMRC Investigation Cost Your Business?

The direct cost of an investigation depends on its complexity and whether professional advisers are involved. For a straightforward aspect enquiry resolved quickly, professional fees in the hundreds to low thousands of pounds are common. For a full enquiry lasting several months, costs can run considerably higher, particularly if the matter proceeds to the First-tier Tribunal.

Beyond professional fees, there is the indirect cost of management time. Gathering records, attending meetings, and corresponding with HMRC takes time away from running your business. For small businesses without a finance team, this burden falls directly on the owner.

If HMRC establishes that additional tax is owed, the unpaid tax plus interest is due regardless of any professional fees incurred. Interest is calculated from the date the tax should have been paid.

Tax investigation insurance and professional cover

Some business owners protect themselves against the cost of professional fees through tax investigation insurance, sometimes called fee protection insurance. This is designed to help cover the cost of your accountant’s time in dealing with an HMRC enquiry, subject to the terms, limits and exclusions of the policy. It does not cover any tax actually owed.

FSB membership includes access to a tax investigation service that may provide professional support if HMRC opens an enquiry into your business, as part of standard membership and subject to FSB’s current terms and conditions. For a small business facing a protracted enquiry, this can be a useful financial protection to have in place.

Your Rights During an HMRC Investigation

The HMRC Charter sets out the standards of behaviour and service that taxpayers can expect, and was last updated in July 2024. As a business owner under investigation, you have rights including:

• HMRC should explain what it wants to check and why
• You can usually appoint an accountant or other authorised adviser to deal with HMRC on your behalf
• You can ask HMRC to clarify what they are asking for and why
• You can appeal decisions you believe are wrong
• The Charter says HMRC will treat customers as honest unless it has reason to think otherwise, and that you should have the opportunity to explain any discrepancies

If you believe HMRC has acted improperly or has not followed its own processes, you can raise a complaint directly with HMRC. If this remains unresolved, you can ask the independent Adjudicator’s Office to look into how HMRC has handled your case.

Practical Steps to Take if You Receive an HMRC Enquiry Letter

• Do not ignore the letter. Failing to respond by the deadline can lead to penalties and unfavourable assumptions
• Read it carefully and note what HMRC is asking for and by when
• Contact your accountant or tax adviser promptly. If you do not have one, consider seeking advice before responding
• Gather the documents HMRC has requested — there is no need to provide more than is asked for
• Be accurate and honest in your responses. Inaccurate information can turn a routine check into a more serious one
• If you need more time, write to HMRC to request an extension before the deadline
• Keep records of all correspondence with HMRC, including dates and the names of any officers you speak with

Good Record-Keeping as Your First Line of Defence

The most effective protection against a difficult HMRC investigation is good record-keeping throughout the year. Businesses that can produce accurate, well-organised records tend to resolve enquiries faster and at lower cost.

How long do you need to keep records?

The rules differ depending on your business structure:

• Self-employed individuals (sole traders and partners): generally at least five years after the 31 January Self Assessment filing deadline for the relevant tax year. For example, records for 2025/26 (due by 31 January 2027) should be kept until at least 31 January 2032
• Limited companies: generally at least six years from the end of the relevant accounting period
• VAT-registered businesses: VAT records generally need to be kept for at least six years, though some VAT schemes have different requirements
• PAYE records for employers: retention periods vary by record type, but employers should generally keep payroll records for several years — check current HMRC guidance for the specific period that applies to each type of record

Many accountants recommend keeping records for around six years as a practical margin, particularly if you file late or have complex entries. If HMRC opens a fraud enquiry, records may be required for longer still.

What records are worth keeping?

• • • Bank statements for all business accounts, including savings and currency accounts.
    • Sales invoices and receipts.
    • Purchase invoices, expenses receipts, and supplier statements.
    • Payroll records, including P11D forms for benefits in kind.
    • VAT records and returns if VAT-registered.
    • Details of any personal funds introduced to or withdrawn from the business.
    • Loan agreements, investment documents, and correspondence relating to significant transactions.

Cloud accounting software can make record-keeping considerably more straightforward and ensures records are not lost if a device fails or an office floods.

How Far Back Can HMRC Investigate?

How far back HMRC can go generally depends on the nature of any error or omission:

• Innocent errors: HMRC can normally go back four years. This is the standard time limit for most routine enquiries
• Careless errors: Where HMRC considers a mistake to have resulted from a lack of reasonable care, the time limit can extend to six years
• Deliberate evasion: Where HMRC suspects deliberate dishonesty or fraud, it can investigate up to twenty years back
• Offshore matters: A separate time limit of up to twelve years can apply in some cases involving undeclared offshore income or assets

These time limits are set out under tax legislation, including the Taxes Management Act 1970. The exact position can depend on the tax involved and the legal power HMRC is using, so if you are concerned about a historic issue it is worth getting tailored advice from an accountant or tax adviser.

Frequently Asked Questions

How will I know if HMRC is checking my tax affairs?

According to GOV.UK, HMRC will call or write to tell you what it wants to check and why. A formal letter will set out the scope of the check and what information is required. Treat all HMRC contact professionally and note the details, even if the first approach is by phone.

Can HMRC investigate me without telling me?

HMRC can gather information from third parties — such as banks, digital platforms, and other government departments — without notifying you. However, to formally open an enquiry into your tax return and request information from you directly, HMRC must notify you in writing.

How far back can HMRC go?

For innocent errors, HMRC can normally go back four years. For careless errors, the time limit is generally six years. Where HMRC considers an error deliberate, it can investigate up to twenty years back, and a separate limit of up to twelve years can apply in some offshore cases. Accurate filing year on year is the most effective protection.

Can HMRC visit my premises?

For most enquiries, HMRC will request records by correspondence and no visit is required. HMRC does have powers to ask to visit business premises for VAT and certain other compliance purposes, usually with notice. Visits without notice or under warrant are uncommon for routine compliance work.

What if I have made genuine errors in previous returns?

Making a voluntary disclosure before HMRC contacts you is generally treated more favourably than errors HMRC discovers independently. Speak to your accountant about whether a voluntary disclosure facility might apply to your situation.

Can I deal with an HMRC investigation myself?

You can, and for straightforward aspect enquiries some business owners do. However, tax investigations can become complex quickly. For any full enquiry, or where significant tax may be in dispute, professional advice is strongly recommended.

Summary

An HMRC investigation is a structured process, not an accusation. Many checks are resolved without any change to the tax due, particularly where a business has kept accurate records and filed its returns honestly.

The key points to take away from this guide are:

• An HMRC check can be triggered by data discrepancies, industry risk factors, or random selection. Being selected does not mean you have done anything wrong
• HMRC must notify you before formally opening an enquiry into your return, and you have rights throughout the process, including the right to appoint an adviser to act for you
• Good record-keeping, accurate returns, and prompt responses are the most effective way to manage an investigation
• Record retention requirements differ by business structure — generally five years for self-employed individuals, and six years for limited companies and VAT records
• The professional cost of dealing with an investigation can be significant. Tax investigation insurance or membership services that include professional representation, subject to their terms and conditions, can help protect a business from unexpected costs
• If you disagree with HMRC’s conclusions, you have the right to appeal and, if necessary, take the matter to the independent First-tier Tribunal

Running a small business involves navigating a range of compliance obligations. Being clear on what an HMRC investigation actually involves means you can respond calmly and effectively if one arises, rather than being caught off-guard.