HMRC enquiry process

What an enquiry is

An HMRC enquiry is a formal review of one or more of your tax returns. It starts with a written notice and ends when HMRC issues a closure notice with their conclusions.

For Self Assessment, HMRC has 12 months from the date you filed to open an enquiry into a return. For Corporation Tax, it's 12 months from the date the return was due. Outside that window, they can only act if a "discovery" applies (typically negligence or error).

What triggers an enquiry

• Random selection — happens to a percentage of returns each year
• Risk profiling — figures that look unusual against industry averages
• Specific anomalies — large round numbers, missing items, big swings vs prior years
• Third-party data — banks, employers, marketplaces share information that doesn't match your return
• Specific campaigns — HMRC sometimes targets specific sectors or behaviours

The process

1. Opening notice: HMRC writes to you, identifying the return and (sometimes) the area of concern. They'll usually request specific records.
2. Information gathering: you provide records and explanations. HMRC may follow up with more questions.
3. Meeting (if needed): for complex enquiries, HMRC may want a face-to-face or phone meeting. You're entitled to representation.
4. Resolution: HMRC writes to confirm their conclusion — agree, propose adjustment, or open formal assessment.
5. Closure notice: the formal end of the enquiry, stating any tax due and any penalty.

How long it takes

Simple enquiries can close in 3-6 months. Complex enquiries — especially those involving multiple years or contested figures — can run for 1-2 years or longer. HMRC sometimes drags; you can apply to the First-tier Tax Tribunal for a closure notice if you think they're being unreasonable.

Practical advice

• Respond by the deadlines HMRC sets — failure to comply with a Schedule 36 information notice carries its own penalties
• Provide what's asked, no more — don't volunteer extra unrequested information
• Keep all correspondence — HMRC, your accountant, your records — in one place
• Consider tax investigation insurance for next year — covers professional fees in defending an enquiry
• Get professional representation if the enquiry feels heavy or escalates

If you spot an error during the enquiry

If you realise you made a mistake on the return, disclose it now — voluntary disclosure during an enquiry significantly reduces the penalty compared with HMRC discovering it themselves. Concealing it makes things much worse.