Not knowing how long it will go on is one of the hardest parts of an HMRC enquiry. Every case is different, but the stages are predictable. Understanding them takes much of the fear out of the process.
A simple compliance check can close within a few months. A full enquiry commonly runs from several months to over a year, and complex COP8 or COP9 cases can take longer. The biggest factor you control is how promptly and completely information is provided.
Opening letter: HMRC explain what they are checking and what they need. Information exchange: you provide records and answers, and HMRC may ask follow-up questions. Meeting (sometimes): in larger cases HMRC may propose a meeting. You don't have to attend, but it can help resolve issues quickly. HMRC's view: the officer sets out their findings and any proposed adjustments. Negotiation: you can challenge the figures, the behaviour category and the penalty reductions. Settlement or closure notice: the case ends with an agreement, a contract settlement or a formal closure notice.
Aspect enquiries into one issue are often resolved within a few months. Full enquiries into a return or a business typically take longer, often six months to a year or more. COP8 and COP9 cases involve reports, meetings and detailed computations and often run beyond a year. These are general patterns, not rules.
late or incomplete replies, which lead to repeated requests disagreement over records that were never kept new issues emerging part-way through long gaps where neither side takes the next step
Respond on time, answer fully, and keep your correspondence organised. If HMRC go quiet for a long time, a polite letter asking for an update or proposing next steps often moves things on. If you feel an enquiry has no good reason to stay open, you can ask the tribunal to direct HMRC to issue a closure notice.
No. You can apply to the First-tier Tribunal for a direction that HMRC close the enquiry, and HMRC must then show reasonable grounds for keeping it open.
Yes. Late payment interest runs on any tax found to be due from the original due date. You can make a payment on account during the enquiry to limit it.
Yes. A compliance check ends with a closure notice or a signed settlement, which confirms the outcome in writing.