What is an HMRC self-assessment enquiry?

An HMRC self-assessment enquiry is a formal investigation into a taxpayer's tax return. HMRC can open an enquiry within 12 months of the filing deadline and can request information, make adjustments, and charge additional tax, interest, and penalties. An HMRC self-assessment enquiry is a formal process by which HMRC investigates a taxpayer's self-assessment tax return. The enquiry process: (1) Opening — HMRC sends a notice of enquiry to the taxpayer (or their agent), stating that an enquiry has been opened into a specific tax year. No reason needs to be given for opening the enquiry. (2) Information requests — HMRC requests information and documents to support the entries on the tax return. The requests can be broad (e.g., all bank statements for the year) or specific (e.g., details of a particular relief claimed). (3) Review — HMRC reviews the information and identifies any issues or discrepancies. (4) Discussion — HMRC discusses the findings with the taxpayer or their agent. The taxpayer can provide explanations, additional information, or challenge HMRC's findings. (5) Closure — the enquiry is closed with a closure notice. If adjustments are made, additional tax may be due, along with interest and potential penalties. The taxpayer can appeal the adjustments to the Tribunal if they disagree. Relevant legislation: TMA 1970, Section 9A (enquiry into self-assessment return); Section 9AB (enquiry into partnership return). Example: A taxpayer files their 2024/25 self-assessment return on 31 January 2026. HMRC can open an enquiry into the return by 31 January 2027 (12 months after the filing deadline). HMRC sends a notice of enquiry in March 2026, requesting bank statements and receipts for business expenses claimed on the return. Common mistake: Ignoring the enquiry notice or not responding promptly. Failing to respond to HMRC's information requests can result in HMRC making assessments based on their own estimates, which are typically much higher than the actual figures.

What is the difference between an aspect enquiry and a full enquiry?

An aspect enquiry focuses on one or more specific aspects of the tax return (e.g., a particular income source or relief). A full enquiry is a comprehensive review of the entire return. Aspect enquiries are more common and generally shorter. HMRC self-assessment enquiries fall into two categories: (1) Aspect enquiry — focuses on one or more specific aspects of the tax return. For example, HMRC may enquire into the business expenses claimed, or the capital gains calculations, without reviewing the entire return. Aspect enquiries are more common and generally shorter, as they focus on specific issues. They can be resolved relatively quickly if the taxpayer can provide satisfactory explanations and documentation. (2) Full enquiry — a comprehensive review of the entire tax return. HMRC reviews all aspects of the return, including all income sources, reliefs, allowances, and deductions. Full enquiries are less common but more extensive, and can take months or even years to resolve. They are typically opened when HMRC has concerns about the overall accuracy of the return or the taxpayer's compliance history. The type of enquiry affects the scope of information requests, the duration, and the potential outcomes. Regardless of the type, the taxpayer should respond promptly and thoroughly, with the assistance of a professional adviser. Relevant legislation: TMA 1970, Section 9A (enquiry into return — no distinction between aspect and full in the legislation, but HMRC practice distinguishes them). Example: An aspect enquiry might focus on the rental income and expenses claimed on a tax return, with HMRC requesting the rental accounts and supporting receipts. A full enquiry would review all income sources (employment, self-employment, rental, investment), all reliefs and allowances, and all deductions, with HMRC requesting comprehensive financial records. Common mistake: Assuming that an aspect enquiry is limited to the specific aspect identified. HMRC can expand an aspect enquiry into a full enquiry if they identify wider issues during the investigation.

How long does an HMRC enquiry take?

The duration varies: aspect enquiries can take a few months, while full enquiries can take 1-2 years or more. There is no fixed time limit for closure, but the taxpayer can apply to the Tribunal for a direction to close the enquiry if it is taking too long. The duration of an HMRC self-assessment enquiry varies significantly: (1) Aspect enquiries — generally shorter, often resolved within 3-6 months if the taxpayer can provide satisfactory explanations and documentation promptly. (2) Full enquiries — can take 1-2 years or more, especially if the taxpayer's affairs are complex or if HMRC identifies significant issues. (3) No fixed time limit — once an enquiry is opened, there is no statutory time limit for closure. HMRC can keep the enquiry open as long as reasonably necessary to complete the investigation. (4) Tribunal direction — if the enquiry is taking too long, the taxpayer can apply to the First-tier Tribunal for a direction that HMRC issue a closure notice. The Tribunal will direct closure if it is satisfied that the enquiry has been open for an unreasonable time or that HMRC is not making progress. (5) Factors affecting duration — the complexity of the taxpayer's affairs, the volume of information requested, the taxpayer's responsiveness, and HMRC's workload all affect the duration. To minimise the duration, the taxpayer should respond to information requests promptly and thoroughly, and engage a professional adviser to manage the enquiry. Relevant legislation: TMA 1970, Section 28 (closure of enquiry); TMA 1970, Section 28A (taxpayer's right to apply to Tribunal for closure direction). Example: An aspect enquiry into rental income and expenses is opened in March 2026. The taxpayer provides the rental accounts and supporting receipts in April 2026. HMRC reviews the information and closes the enquiry in June 2026 (3 months). A full enquiry opened in March 2026 might take until late 2027 to resolve, depending on the complexity. Common mistake: Not applying to the Tribunal for a closure direction when the enquiry is taking too long. The taxpayer has the right to apply, and the Tribunal can direct HMRC to close the enquiry if it has been open for an unreasonable time.

What information can HMRC request during an enquiry?

HMRC can request any information and documents that are reasonably required to check the accuracy of the return. This includes bank statements, receipts, invoices, contracts, and accounting records. The requests must be reasonable and relevant. During a self-assessment enquiry, HMRC can request information and documents that are reasonably required to check the accuracy of the return. The scope of information requests: (1) Statutory information powers — HMRC has statutory powers to request information and documents under TMA 1970, Schedule 36. The information must be 'reasonably required' for the purpose of checking the taxpayer's tax position. (2) Types of documents — common requests include: bank statements and building society statements, receipts and invoices for expenses claimed, contracts and agreements (e.g., rental agreements, employment contracts), accounting records and books of account, details of capital gains calculations, and personal financial records. (3) Reasonableness — the requests must be reasonable and relevant to the enquiry. HMRC cannot make 'fishing expeditions' — requests for information that are not relevant to the specific tax position under enquiry. (4) Challenge — the taxpayer can challenge information requests that are unreasonable, irrelevant, or disproportionate. If HMRC insists, the taxpayer can appeal to the Tribunal. (5) Penalties for non-compliance — if the taxpayer fails to provide the requested information without a reasonable excuse, HMRC can charge penalties. The penalties can be significant (up to £60 per day for continuing failure). The taxpayer should provide the requested information promptly and thoroughly, but should also ensure that the requests are reasonable and relevant. Relevant legislation: TMA 1970, Schedule 36 (information and inspection powers); TMA 1970, Schedule 36, Paragraph 45 (penalties for non-compliance). Example: During an enquiry into a taxpayer's self-employment income and expenses, HMRC requests: bank statements for the tax year, sales invoices, purchase receipts, mileage records, and the accounting records. These are reasonable and relevant to checking the accuracy of the self-employment entries on the return. HMRC requests bank statements for a different tax year (not under enquiry) — this may be unreasonable and challengeable. Common mistake: Providing more information than requested, without considering whether the requests are reasonable and relevant. While it is important to be cooperative, providing excessive information can give HMRC additional leads and prolong the enquiry.

What happens at the end of an HMRC enquiry?

The enquiry is closed with a closure notice. If adjustments are made, additional tax may be due, along with interest and potential penalties. The taxpayer can appeal the adjustments to the Tribunal if they disagree. The enquiry is closed with a closure notice issued by HMRC. The outcomes can vary: (1) No adjustments — if HMRC is satisfied with the return, the enquiry is closed with no adjustments. No additional tax, interest, or penalties are due. (2) Adjustments — if HMRC identifies errors or omissions, adjustments are made to the return. This may result in additional tax being due. (3) Interest — interest is charged on any additional tax, from the original due date to the date of payment. (4) Penalties — if the errors were due to careless behaviour or deliberate behaviour, penalties may be charged. Penalties range from 0% (for unprompted disclosure of careless errors) to 100% of the additional tax (for deliberate and concealed errors). (5) Appeal — if the taxpayer disagrees with the adjustments, they can appeal to the First-tier Tribunal within 30 days of the closure notice. The Tribunal will review the case and make a determination. (6) Repayment — if the adjustments result in a reduction in tax (e.g., the taxpayer overpaid), HMRC will repay the excess tax with interest. The taxpayer should carefully review the closure notice and the proposed adjustments, and seek professional advice before accepting the outcome or appealing. Relevant legislation: TMA 1970, Section 28 (closure of enquiry); TMA 1970, Section 29 (assessments); FA 2007, Schedule 24 (penalties); TMA 1970, Section 31 (appeals). Example: An enquiry into a taxpayer's rental expenses results in HMRC disallowing £5,000 of expenses claimed. The closure notice adjusts the return, resulting in additional tax of £2,000 (40% of £5,000), plus interest of £200, plus a penalty of £600 (30% for careless behaviour). Total payable: £2,800. The taxpayer can appeal the adjustments to the Tribunal if they disagree. Common mistake: Accepting the closure notice and adjustments without seeking professional advice. An experienced tax adviser can review the adjustments, challenge errors, and negotiate a better outcome.

Tax Disputes › Enquiries

HMRC Self-Assessment Enquiries

HMRC can open an enquiry into your self-assessment tax return. Understand the enquiry process, your rights, and how to respond effectively to minimise risk and achieve the best outcome.

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An HMRC self-assessment enquiry is a formal investigation into a taxpayer's tax return. HMRC has wide-ranging powers to open enquiries, request information and documents, and make assessments. Understanding the enquiry process, your rights, and how to respond effectively is essential for achieving the best outcome and minimising the risk of penalties and additional tax.

Types of Enquiry

HMRC can open two types of enquiry: (1) Aspect enquiry — focuses on one or more specific aspects of the tax return (e.g., a particular source of income or relief claimed). (2) Full enquiry — a comprehensive review of the entire tax return. Aspect enquiries are more common and generally shorter, while full enquiries are more extensive and can take years to resolve.

The Enquiry Process

The enquiry process follows these steps: (1) Opening notice — HMRC sends a notice of enquiry to the taxpayer, stating that an enquiry has been opened. (2) Information requests — HMRC requests information and documents to support the return. (3) Review and analysis — HMRC reviews the information and identifies any issues. (4) Discussion — HMRC discusses the findings with the taxpayer or their agent. (5) Closure — the enquiry is closed with a closure notice, which may include adjustments to the return, additional tax, interest, and penalties.

Time Limits

HMRC can open an enquiry within 12 months of the filing deadline (i.e., by 31 January following the tax year for returns filed on time). For returns filed late, the enquiry window is extended to the quarter day following the first anniversary of the filing date. Once the enquiry is opened, there is no fixed time limit for closure, but the taxpayer can apply to the Tribunal for a direction to close the enquiry if it is taking too long.

Your Rights

During an enquiry, the taxpayer has several rights: (1) To be informed of the reasons for the enquiry (on request). (2) To have the enquiry conducted reasonably and efficiently. (3) To challenge HMRC's findings and assessments. (4) To appeal to the Tribunal if the enquiry is not closed or if the taxpayer disagrees with the adjustments. (5) To be represented by a professional adviser.

Key Points

What You Need to Know

HMRC can open an enquiry within 12 months of the filing deadline
Aspect enquiries focus on specific items; full enquiries review the entire return
HMRC can request information and documents to support the return
The enquiry is closed with a closure notice, which may include adjustments and penalties
Taxpayers can appeal to the Tribunal if they disagree with HMRC's findings

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