Guide
How long does a tax investigation take?
Updated
Length tracks scope: a question about one entry is answered in weeks, a full review of a return takes months, and complex cases run longer. The pace is partly in your control, which is the useful part.
Typical durations, honestly framed
| Enquiry type | Commonly observed duration |
|---|---|
| Single-aspect enquiry | A few weeks to a few months |
| Full enquiry into a return | Several months to a year, sometimes longer |
| Complex or COP8/COP9 cases | Commonly a year or more, scoped per case |
These are patterns, not promises: HMRC does not publish target durations for enquiries, and a single unanswered letter can add months. Treat the table as planning context and your adviser's estimate, once they have seen the file, as the better figure.
What sets the pace
- Scope: one queried figure closes quickly; "send us the business records" takes as long as the records take.
- Response quality: complete, organised answers close points; partial answers generate follow-up letters, and each round trip costs weeks.
- Whether new issues surface: an enquiry that finds something can widen; one that finds order tends to narrow.
- HMRC's own workload: replies from HMRC can themselves take weeks; quiet periods are normal and rarely mean anything.
Shortening it
- Respond by the dates in the letters, or ask for more time before the date, not after.
- Answer what was asked, completely and once: the goal is closing questions, not winning them.
- If it has run over a year without clear reason, an adviser can ask HMRC to close or narrow the enquiry; there is a formal route to request closure through the tribunal, which specialists use sparingly but effectively.
HMRC's own overview of compliance checks (gov.uk) explains the process and your rights during it, including that you can have an adviser act for you at any stage. Nothing here is tax advice; see what representation costs.