There is no statutory clock on an HMRC investigation: no rule sets a date by which a compliance check must finish. How long one takes is decided by four things: how wide the check is, how quickly and completely HMRC's questions are answered, whether the figures end up in dispute, and the route by which it closes. A narrow question about one entry on one return can be dealt with in an exchange of letters; a full review of a business's records, or a case where HMRC suspects deliberate behaviour, is a different undertaking altogether. GOV.UK's compliance checks guidance sets out the framework. For how the compliance check process itself works, see our guide to HMRC's compliance check service. Correct as at 13 August 2026.
What decides how long a check takes?
Scope is the biggest lever, and it is set by HMRC's opening letter: one aspect of one return, or everything. The rest is largely in your hands. The table sets out what tends to move the timetable in each direction.
| Factor | Tends to shorten the check | Tends to lengthen it |
|---|---|---|
| Scope | A single aspect of a single return | Full returns, several years, or connected company and personal affairs |
| Records | Complete, organised, reconciled | Missing, reconstructed, or contradicting the returns |
| Responses | Prompt, complete answers through one channel | Late or partial replies that invite follow-up rounds |
| The figures | Agreed or narrowed early | Disputed valuations, estimates or behaviour arguments |
| Behaviour | An error accepted and corrected | Suspected deliberate conduct, which changes the process itself |
What are the stages of an HMRC compliance check?
Most checks move through the same sequence:
- An opening letter saying what HMRC is checking and asking for information or documents
- Review rounds: HMRC works through what you send and comes back with questions
- Meetings or visits: HMRC may ask to visit your home, business or your adviser's office, or ask you to visit them, and you can have an accountant or legal adviser with you at a visit (both points are in GOV.UK's guidance)
- A position: HMRC sets out what it thinks the right figures are and why
- Closure: agreement or amended assessments, penalties where they are due, and your rights if you disagree
The cycle in the middle is where time is won or lost. Every incomplete answer buys another round.
What can HMRC ask you for?
The opening letter usually asks for information and documents relevant to what is being checked: business records, bank statements, invoices, working papers behind a return. Relevance is the boundary that matters. A check into one year's property pages is not an open door to a decade of personal bank statements, and part of an adviser's job is holding requests to the scope HMRC itself has defined, politely and in writing.
Visits follow the same logic. GOV.UK's guidance is explicit that HMRC may ask to visit your home, business or adviser's office, or ask you to come to them, and that you can have an accountant or legal adviser with you. A visit is rarely the first step, and where one is proposed, the venue, the agenda and who attends are all things to settle in advance rather than improvise on the day.
Two behaviours slow checks down more than any tactic: guessing (an answer that later needs correcting reopens settled ground and dents credibility on everything else) and over-supplying (handing over more than was asked invites questions the check never contained). Answer what was asked, fully, evidenced, once.
Can you speed an investigation up?
You cannot set HMRC's pace, but you can remove every reason for delay on your side. Respond by the dates given, completely. Keep one channel: a single adviser dealing with HMRC beats parallel correspondence. Volunteer the reconciliation rather than the raw records, so HMRC reviews an analysis instead of building one. And ask, in writing, what remains open once you have answered: it keeps the check honest about its own scope.
If you reach deadlock, HMRC's closing decisions are not the end of the road: assessments and penalty decisions carry rights of review and appeal, with deadlines that matter.
When does an enquiry become serious?
Watch for the scope widening from one aspect to whole returns, questions shifting from what happened to why it happened, requests reaching back across more years, or any mention of Code of Practice 8 or 9. Those are the markers of an investigation changing character. Our Code of Practice 9 page explains the serious-fraud procedure, and our guide to how far back HMRC can investigate covers the time limits that open up as behaviour worsens.
Example
Example. Two checks, two shapes. First, a company receives a full enquiry into a year's return: sales cut-off, directors' loans and expenses are all in scope. Its records are complete but scattered across systems, so the adviser's first move is assembling one reconciled bundle before answering anything, and the check proceeds in defined rounds: information, questions, a meeting at the adviser's office, positions exchanged, figures agreed. The scope was wide, so the check was long; it was never allowed to become open-ended, because every HMRC letter got a complete answer and a written question back: what remains open?
Second, a landlord receives a check into the property pages of one return. With her adviser she assembles the letting statements, the mortgage interest certificates and a bank reconciliation, and finds the deposit HMRC had matched against her account was a tenancy deposit later repaid, not rent. The adviser sends the reconciliation with a short covering analysis answering each question in HMRC's letter, and invites any remaining questions in one list. HMRC raises one follow-up on repairs, accepts the evidenced answer, and closes the check with no change. The same check handled with drip-fed bank statements and unanswered questions would have run to many more rounds, whatever the underlying facts.
What to do now
Answer the letter in front of you fully and by its date. Assemble the records for the years and entries named before deciding anything. Instruct one adviser to run the channel to HMRC, and do not guess answers you can evidence next week instead. If the letter hints at behaviour, or mentions COP8 or COP9, treat it as urgent and take advice before replying at all: our tax investigations page explains how we take these over, including part-run enquiries that have stalled.
Frequently Asked Questions
HMRC has a limited window to open an enquiry into a filed return, and separate, longer time limits to assess tax it believes was lost. Those limits stretch as the behaviour involved worsens, from ordinary error through carelessness to deliberate conduct. Our guide to how far back HMRC can investigate covers the detail.
HMRC may ask to visit your home, business premises or your adviser's office, or ask you to visit them. You can have an accountant or legal adviser with you during a visit, and the adviser's office is often the sensible venue. How a visit request is handled is worth agreeing with your adviser before you reply.
For a narrow query about one figure, some people do. The case for an adviser strengthens quickly as the scope widens, more years are pulled in, or the questions move from the figures to your behaviour, because answers given early bind the rest of the check.
Closing decisions, amended assessments and penalties carry rights of review and appeal, and the deadlines for using them are short. Disagreeing is a process, not a stand-off: set out the evidence, use the review, and take advice on whether the tribunal route is worth it.
No. Representation is routine, GOV.UK's guidance covers authorising an agent for a check, and HMRC deals with advisers every day. What an adviser changes is the quality and completeness of each response, which is the main thing that shortens a check from the taxpayer's side.
Talk to us about a live check
If a compliance check has opened, or one has stalled, speak to Ghulam Alahi, Managing Director, who has more than 25 years' experience in HMRC enquiry work. The first conversation covers what HMRC has asked for, what actually needs to be provided, and how to shorten the road from here. Call 020 8554 2135 or email info@visionconsulting.co.uk, or use our contact page.
By the Vision Consulting team.
This is general information, not advice. Your position depends on your circumstances.