Compliance
HMRC Enquiry Guide
An HMRC enquiry is a formal check of a tax return or tax position. Understanding what triggers one, how the process works and what your rights are helps you respond effectively and avoid making things worse.
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Quick answer
What are the key takeaways?
HMRC can open an enquiry into a Self-Assessment or Corporation Tax return within 12 months of the filing date.
Key takeaways
HMRC can open an enquiry into a Self-Assessment or Corporation Tax return within 12 months of the filing date.
Enquiries can be random, aspect-based (targeting one area) or full (covering the whole return).
HMRC cannot simply demand documents — there are formal information powers and a right of appeal.
Professional representation significantly improves outcomes and reduces the risk of unnecessary disclosures.
What triggers an HMRC enquiry?
Some enquiries are selected at random and there is little you can do to avoid them. Others are triggered by statistical anomalies — for example, expenses that appear unusually high relative to turnover for your sector, income that does not match third-party data HMRC holds, or large year-on-year fluctuations.
Late filings, amended returns, new sources of income, certain business sectors and connected-party transactions can also increase enquiry risk. HMRC also receives information from banks, employers, letting agents, HMRC Connect and other sources that may not match what a return shows.
What types of enquiry does HMRC use?
A full enquiry covers the entire tax return and is used where HMRC suspects significant underreporting. An aspect enquiry targets a specific line or category — for example, a particular expense claim or a disposal of assets. A random enquiry has no specific trigger and is used as a compliance check.
HMRC also conducts Code of Practice 9 (COP9) investigations for suspected serious fraud and Code of Practice 8 (COP8) investigations for complex tax avoidance. These are more serious than routine enquiries and require immediate specialist advice.
What are your rights during an enquiry?
HMRC must open an enquiry by written notice within the statutory enquiry window — generally 12 months from the date the return was filed (longer for late or amended returns). You are entitled to know what aspect is being investigated.
HMRC can issue formal information notices requiring documents, but you can appeal against a notice to the Tax Tribunal if requests are disproportionate. You also have the right to a statutory review by a separate HMRC officer and to appeal to the First-tier Tribunal if you disagree with an HMRC decision.
How far back can HMRC go?
Outside a live enquiry window, HMRC can generally assess up to four years back for an innocent error, six years where the error was careless, and twenty years where it was deliberate. HMRC needs a reason to look beyond four years, which is why the behaviour behind an error matters as much as the figure.
HMRC can ask for bank statements, invoices, receipts, payroll records, contracts, bookkeeping exports and explanations of specific transactions — but only records relevant to the period and point under review. Send what answers the question asked, organised so the trail from source document to return is easy to follow.
What should you do when the letter arrives?
Check which tax, period and return HMRC is reviewing, and record the response deadline — ignoring the letter or missing the date makes the process harder. Send the letter to your accountant before drafting any reply, gather the original records in one secure folder with clear names and dates, and keep a copy of every response and document supplied.
Do not send more than HMRC has asked for. A focused, well-explained answer to an aspect enquiry keeps it an aspect enquiry; an unprompted bundle of extra records can widen it.
How do you prepare before HMRC ever asks?
Preparation is a bookkeeping discipline: keep business records for at least six years, reconcile bank accounts regularly so returns agree to the underlying records, note the reason for one-off or unusual transactions when they happen, and file accurately and on time. Cloud accounting software keeps the evidence backed up and searchable.
A trigger does not prove a return is wrong — businesses have unusual years. The task in an enquiry is to show the records and the commercial reason behind the figures, which is far easier when the explanation was written down at the time rather than reconstructed months later.
Why does professional representation matter?
Responding to an HMRC enquiry without advice can lead to unnecessary disclosures, admissions that are used against you in other years or a wider investigation than HMRC was entitled to pursue.
An accountant or tax adviser who is experienced in enquiries can manage correspondence with HMRC, ensure responses are factually accurate and appropriately scoped, negotiate settlements and represent you before the Tax Tribunal if necessary.
Questions
What do people ask about hmrc enquiry guide?
These answers cover the practical points clients commonly raise before asking Countify to review their own position.
Ask a different questionHow long can an HMRC enquiry last?
There is no fixed time limit. Simple aspect enquiries may conclude within a few months; complex full enquiries or fraud investigations can run for years. Keeping good records and responding promptly tends to shorten the process.
Can HMRC investigate years that were not queried in the original enquiry notice?
Not automatically. HMRC can only enquire into a return within the relevant enquiry window. However, if fraud or careless behaviour is established, HMRC can go back up to 6 or 20 years respectively, so the stakes of a current enquiry can affect earlier years.
What should I do if I receive an HMRC enquiry notice?
Do not respond until you have sought professional advice. Check the notice is within the correct enquiry window, identify what is being asked and appoint an accountant or tax adviser to manage the correspondence on your behalf.
Can Countify handle an HMRC enquiry on my behalf?
Yes. Countify can represent clients during HMRC enquiries, manage correspondence, organise the required records and negotiate outcomes where appropriate.
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