HMRC Investigation Letter: What Should You Do First?

Few letters create more immediate anxiety for a business owner than one carrying the HMRC logo and the words “compliance check”, “enquiry” or “investigation”.

It is natural to fear the worst. You may begin wondering whether an innocent bookkeeping mistake has become a serious problem, whether HMRC already has information about your business or whether a large tax bill is about to follow.

The arrival of a letter does not automatically mean HMRC has decided that you did something wrong. A compliance check sometimes called a tax enquiry—is a process HMRC uses to examine whether the correct tax has been paid and whether allowances, expenses and reliefs have been claimed properly.

However, the way you respond at the beginning can significantly affect the length, scope and potential cost of an HMRC tax investigation. Ignoring the letter is dangerous, but replying hastily without reviewing the facts can be equally damaging.

The correct first step is to remain calm, protect your records and obtain professional advice before providing a detailed response.

Do Not Panic but Do Not Ignore the Letter

An HMRC investigation letter should be taken seriously, but panic often leads to poor decisions. Business owners sometimes telephone the investigating officer immediately and begin answering questions without checking their records. Others become overwhelmed and leave the letter unanswered until the deadline has passed.

Neither approach is helpful.

Start by reading the entire letter, including every attachment and factsheet. Identify the tax being examined, the accounting period involved, the information requested and the response deadline. Make a note of the investigating officer’s name, telephone number, office address and case reference.

HMRC confirms that a compliance check may examine whether tax has been paid at the right time and whether the correct allowances and reliefs have been claimed. Its compliance-check guidance also states that taxpayers should continue filing returns and paying other taxes due while a check is taking place.

The letter should not be left at the bottom of a paperwork pile. Treat the response date as an immediate business deadline.

First, Confirm That the Letter Is Genuine

Fraudsters frequently imitate HMRC correspondence, so authenticity should be checked before sensitive financial information is disclosed.

Examine the letter for your correct name, tax reference, case number and details of the HMRC team involved. If anything appears suspicious, verify the contact using independently sourced details from GOV.UK rather than relying solely on a telephone number or QR code printed on the letter.

HMRC provides an online service to check whether a letter is genuine. If a suspicious letter is not listed, HMRC advises contacting the relevant department named in the correspondence.

Never provide Government Gateway credentials, passwords or banking security codes in response to unexpected contact. If the correspondence is fraudulent, report it through HMRC’s official scam-reporting service.

Verifying the letter should happen quickly so that a genuine enquiry deadline is not missed.

Understand What Type of HMRC Letter You Have Received

Not every HMRC letter represents the same level of risk. The wording and legal basis of the correspondence matter.

A general compliance check may focus on one tax return, a particular expense claim, VAT repayment, payroll issue or discrepancy between declared income and information held by HMRC. Other enquiries may examine the wider business records and several accounting periods.

A letter might contain an informal request for information, while another may include a formal information notice requiring specified documents by a particular date. The recipient’s obligations and appeal rights can differ significantly.

Some letters are described as “nudge letters”. These may indicate that HMRC holds information suggesting a possible omission and is inviting the taxpayer to review their position. A nudge letter should not be dismissed merely because it does not formally open a full enquiry.

Letters referring to Code of Practice 9, the Contractual Disclosure Facility, suspected fraud or a possible criminal investigation are exceptionally serious. HMRC’s Code of Practice 9 guidance explains that the Fraud Investigation Service uses this process where fraud is suspected.

Anyone receiving such correspondence should obtain specialist tax investigation and, where appropriate, legal advice before responding or signing any document.

Contact an Accountant Before Giving a Detailed Response

One of the safest early actions is to send the complete letter and all attachments to an experienced accountant or tax adviser.

Do not provide only the first page or a summary from memory. Small details within the wording may reveal whether HMRC is testing a particular transaction, comparing third-party information or seeking to expand the scope of the enquiry.

An adviser can examine whether the request is clear, relevant and legally valid. They can also review the deadline, contact the investigating officer, request clarification and determine whether additional time is reasonably needed.

You can formally authorise an accountant or tax adviser to communicate with HMRC on your behalf. HMRC’s agent-authorisation guidance confirms that taxpayers can appoint an agent to manage their tax affairs.

Professional representation does not make the issue disappear, but it can prevent avoidable statements, inconsistent explanations and unnecessary disclosure of unrelated information.

Preserve Every Relevant Record Immediately

Once an investigation begins, protect all documents that could relate to the tax period or transactions under review.

This may include bank statements, invoices, receipts, accounting software data, payroll records, VAT returns, CIS records, contracts, loan agreements, dividend documentation, mileage logs, till records, emails and correspondence with customers or suppliers.

Create secure backups of digital accounting records and preserve the original information. Do not delete transactions, rewrite descriptions, alter invoices or manufacture documents retrospectively. If a record is missing, note the problem and attempt to obtain a replacement from the bank, supplier or other independent source.

Reconstructed records should be clearly identified as reconstructions. They should never be presented as original documents.

Business owners sometimes begin “tidying up” their accounting software after receiving an HMRC letter. Although correcting genuine bookkeeping errors may eventually be necessary, altering historical records before preserving the original data can make it harder to explain what happened and when.

The safest approach is to freeze a reliable copy of the existing records before any adjustment is made.

Do Not Telephone HMRC Unprepared

The investigating officer may invite you to call. A professional conversation can be useful, but an unprepared telephone call creates risks.

Business owners under pressure may guess dates, estimate figures or offer explanations that later conflict with the documentary evidence. They may also answer questions extending beyond the original scope without understanding why the information is being requested.

If HMRC calls unexpectedly, you can take the officer’s details and explain that you wish to consult your adviser before discussing the case. If you are uncertain that the call is genuine, end it politely and verify the officer through official HMRC channels.

You should never deliberately mislead HMRC. The objective is to ensure that any answer provided is accurate, considered and supported by the available evidence.

Review the Tax Returns Before Answering HMRC

Before preparing the formal response, the relevant returns should be compared with the underlying accounting records.

For a sole trader, this might include reconciling declared turnover with bank deposits, card payments, online marketplaces and cash sales. For a limited company, the review may also cover director’s loan transactions, dividends, payroll, business expenses and differences between statutory accounts and the Company Tax Return.

A VAT investigation may require examination of VAT codes, sales invoices, purchase invoices, reverse-charge transactions, zero-rated sales and input tax claims. A CIS enquiry might involve contractor returns, subcontractor verification, deductions and employment-status questions.

The review should extend beyond the specific figure mentioned in the letter if connected transactions could affect the explanation. An adviser needs to know about genuine mistakes before replying to HMRC—not after contradictory documents have been submitted.

This internal review is not about creating a defence at any cost. It is about establishing the true facts and responding from an informed position.

Build a Clear Timeline of Events

HMRC enquiries often become difficult because the business owner remembers the general situation but cannot explain when individual events occurred.

A written timeline can establish when the business began trading, when invoices were raised, when payments were received, when assets were purchased and who prepared each return. It can also identify changes in accountants, accounting software, bank accounts or business structure.

If an unusual transaction caused the enquiry, the timeline should record the commercial purpose, parties involved, supporting agreement and accounting treatment.

A clear chronology helps the adviser identify missing evidence and ensures that written explanations remain consistent with the documents.

Check Exactly What HMRC Is Asking For

An HMRC request may appear simple but contain broad phrases such as “all supporting records”, “full details” or “any other relevant information”.

Before supplying documents, identify precisely what is required and why. The response should be complete and cooperative, but it should also be organised and relevant to the enquiry.

Submitting thousands of unreviewed files can create confusion and potentially expose unrelated issues that were not part of the original check. On the other hand, withholding required documents or deliberately providing an incomplete response can lead to formal notices, penalties and a wider investigation.

HMRC can issue information or inspection notices and may charge penalties where a person fails to comply without a reasonable excuse. HMRC’s tax compliance check guidance confirms that taxpayers may have an accountant or legal adviser present during a visit.

Certain information-notice requirements may carry appeal rights, while others may not. A professional adviser should review the notice rather than assuming it must either be accepted completely or refused.

What If You Cannot Meet the Deadline?

Do not wait until the final day before asking for more time.

If the request is extensive, records must be obtained from third parties or the relevant person is ill or unavailable, contact the investigating officer as soon as possible. Explain why additional time is required and propose a realistic response date.

HMRC is not obliged to approve every extension, but an early and reasonable request is more likely to be considered constructively than silence followed by a missed deadline.

Keep written evidence of any extension agreed. If the discussion takes place by telephone, follow it with a letter or email confirming your understanding.

Where the correspondence includes a formal information notice or appeal deadline, specialist advice should be obtained immediately because statutory time limits may apply.

Should You Tell HMRC If You Discover an Error?

If the internal review identifies an error, tell your adviser immediately. Do not conceal it and do not attempt to correct it informally without considering the wider investigation.

The adviser should determine whether the error affected tax, how it occurred, which periods are involved and whether connected mistakes exist. The correct response may require revised calculations, an amended return, a formal disclosure or an explanation within the enquiry correspondence.

HMRC distinguishes between errors that are careless, deliberate or deliberate and concealed. This classification can have a significant effect on penalties.

Cooperation may also influence the penalty position. HMRC states that it considers the taxpayer’s level of cooperation when determining whether a penalty can be reduced. Its inaccuracy penalty guidance considers the quality of disclosure, including telling HMRC about the issue, helping quantify it and providing access to relevant records.

Cooperation does not mean agreeing with every HMRC assumption. It means being truthful, responsive and properly prepared.

The Most Dangerous Mistakes to Avoid

Do not ignore the letter, miss deadlines deliberately or assume HMRC will lose interest. Do not destroy, hide or alter records. Do not invent explanations, backdate documents or ask an employee to change their account of events.

Avoid sending an emotional response accusing HMRC of targeting the business unfairly. The enquiry should be handled using evidence, calculations and clear professional communication.

Do not provide guesses simply because an officer expects an immediate answer. Where information is uncertain, say that the records are being reviewed and provide a confirmed response later.

Most importantly, do not hide relevant facts from your own accountant. An adviser who receives only part of the story may unintentionally send HMRC an explanation that is contradicted by documents or information HMRC already possesses.

Does an Investigation Mean HMRC Already Has Evidence?

HMRC may open a check for several reasons. A return may contain figures that appear inconsistent, a VAT repayment may look unusual, or information from another source may not match the taxpayer’s declaration.

HMRC may hold information from employers, banks, online platforms, government departments, overseas tax authorities or other businesses. However, an enquiry can also begin without evidence of deliberate wrongdoing.

An investigation letter rarely explains everything HMRC knows. Attempting to guess the source can distract from the essential task: reviewing the records and establishing whether the submitted tax position was correct.

Assume that explanations may be compared with independent data and ensure every response is accurate.

How Long Does an HMRC Tax Investigation Take?

There is no fixed duration. A focused enquiry involving one clear question may be resolved relatively quickly if the records are complete and the explanation is straightforward.

A wider investigation can continue for many months, particularly where several taxes, accounting periods or related parties are involved. Delays can also arise where records are missing, calculations are disputed or information must be obtained from third parties.

Prompt, organised responses can help move a case forward, but speed should not come at the cost of accuracy. An adviser should monitor outstanding questions, maintain a correspondence timeline and request formal closure when HMRC’s enquiries have been answered.

What Could the Investigation Cost?

The outcome may be that the original tax return was correct and no additional tax is due. If errors are discovered, HMRC may seek unpaid tax, late-payment interest and penalties.

The penalty position depends on the type of error, why it happened, whether HMRC prompted the disclosure and how the taxpayer cooperated. Deliberate behaviour is generally treated more seriously than a careless mistake, while reasonable care may provide a defence against certain inaccuracy penalties.

Professional fees will also depend on the scope and duration of the enquiry. Early advice may appear like an additional expense, but it can prevent poor responses from creating unnecessary work or expanding the investigation.

How SAS Yorkshire Can Help

Receiving an investigation letter can make a business owner feel isolated, particularly when the language is technical and the deadline is approaching.

SAS Yorkshire provides practical HMRC enquiry help Yorkshire businesses can rely on. The team can review the opening letter, identify the type and scope of the check and examine the relevant accounting and tax records before a response is submitted.

Support may include preparing reconciliations, gathering evidence, reviewing tax returns, communicating with the HMRC officer and helping the business answer questions clearly and accurately. Where mistakes are identified, SAS Yorkshire can assist in calculating the tax effect and presenting an appropriate disclosure.

If the letter involves suspected fraud, Code of Practice 9 or a potential criminal matter, the business may require specialist investigation and legal representation. SAS Yorkshire can help identify the seriousness of the correspondence promptly so the appropriate professional support can be arranged.

The sooner the letter is reviewed, the more time there is to protect the business’s position.

Take Control Before You Reply

An HMRC letter does not need to create immediate chaos. The situation becomes more manageable when the business verifies the correspondence, records the deadline, preserves its documents and obtains professional advice.

The first response should be based on facts rather than fear. It should answer HMRC’s legitimate questions without speculation, inconsistency or unnecessary information.

If an HMRC tax investigation letter has arrived, do not leave it unanswered and do not respond in haste.

Contact SAS Yorkshire for confidential HMRC enquiry help in Yorkshire. Send the complete letter and attachments to the team as soon as possible so the position can be reviewed before the response deadline.

This article provides general information and is not a substitute for advice based on the specific letter, tax, period and circumstances involved.

Frequently Asked Questions

1. Does an HMRC investigation letter mean I am suspected of fraud?

Not necessarily. HMRC conducts compliance checks to confirm that returns are accurate and that the correct tax has been paid. An enquiry may result from an unusual figure, information mismatch, repayment claim or routine risk assessment. However, correspondence referring to fraud, Code of Practice 9 or the Contractual Disclosure Facility is much more serious and requires urgent specialist advice.

2. Should I call HMRC as soon as the letter arrives?

You should act immediately, but that does not always mean giving HMRC a detailed telephone response straight away. First verify that the letter is genuine, identify the deadline and allow your accountant or adviser to review the correspondence. An unprepared call can produce guesses or inconsistent explanations. If contact is necessary, it should be planned and based on the available records.

3. Can my accountant deal with the investigation for me?

Yes. An authorised accountant or tax adviser can communicate with HMRC, prepare written responses and attend meetings or visits. You will still need to provide complete and honest information to the adviser and may occasionally need to answer questions personally. Professional representation helps ensure that HMRC receives organised, evidence-based responses.

4. What happens if my records are incomplete?

Tell your adviser immediately and begin obtaining replacements from banks, suppliers, customers, payroll providers and software systems. Where original records cannot be recovered, calculations may need to be reconstructed using reliable evidence. The reconstruction and its limitations should be explained honestly. Never create false invoices or present newly prepared documents as originals.

5. Can an accountant get an HMRC investigation closed?

An accountant cannot guarantee that HMRC will close an enquiry or accept a particular conclusion. They can review whether HMRC’s questions have been answered, challenge unsupported assumptions, provide evidence and request formal closure at the appropriate time. Strong records and clear professional communication can help prevent an enquiry from continuing unnecessarily.