Surviving an HMRC Investigation: Professional Defence Strategies

A letter from HMRC opening an enquiry, compliance check, or investigation triggers a particular kind of dread. The letter rarely explains itself in detail. The next step is unclear. And the temptation is either to over-engage (volunteering everything immediately, weakening any future negotiating position) or to under-engage (delaying responses, escalating the situation). Neither is right. There is a structured response framework for each level of HMRC scrutiny, and the framework materially affects how the case ends.

This guide covers the spectrum of HMRC scrutiny, from routine compliance checks through formal enquiries to COP8 and COP9 fraud-suspected investigations. Each has different powers, different procedural protections, and different exit routes.

The spectrum of HMRC scrutiny

Not every HMRC letter is an investigation. The spectrum runs from routine to serious:

1. 1Routine information request: HMRC asks for clarification on a specific point. Usually resolves with a clear, evidenced response.
2. 2Compliance check: HMRC selects a return for review. Can become an enquiry or close with no adjustment.
3. 3Section 9A enquiry: formal opening of an investigation into a specific year's return. Time-limited and procedurally structured.
4. 4Discovery assessment: HMRC issues an assessment for a year not currently in time-limit through normal enquiry, citing discovery of new information.
5. 5COP8 (Code of Practice 8): investigation where HMRC suspects tax avoidance schemes have been used.
6. 6COP9 (Code of Practice 9): investigation where HMRC suspects deliberate tax fraud and offers the Contractual Disclosure Facility.
7. 7Criminal investigation: rare but possible where evidence of deliberate fraud is substantial. Conducted by HMRC's Fraud Investigation Service.

What triggers an HMRC compliance check

HMRC selects returns for compliance check using a combination of risk-based algorithms and random sampling. The most common triggers:

• Mismatch between HMRC's third-party data (PAYE, banks, Land Registry, letting platforms) and what was declared.
• Industries flagged as high-risk for the year (rotating focus on different sectors).
• Unusual fluctuations in declared income, expenses, or specific claims year-on-year.
• High-value reliefs claimed (R&D, SEIS/EIS, certain CGT exemptions).
• Late or amended returns above a certain materiality threshold.
• Specific information from third-party reports (employer disclosures, customer complaints, whistleblowers).
• Random selection (a small percentage of returns each year are selected without any specific risk flag).

How far back HMRC can actually go

HMRC's power to make assessments is bounded by the Taxes Management Act 1970 and the Finance Act 2008. The time limits depend on the nature of the non-compliance:

The categorisation of behaviour drives both the time limit and the penalty band. A meaningful part of investigation defence is establishing that the behaviour was at the lower end of the spectrum (innocent or careless rather than deliberate), which both shortens the time HMRC can pursue and reduces the penalty multiplier.

What HMRC inspectors can and cannot do

HMRC has substantial information-gathering powers but they are not unlimited. What inspectors can do:

• Request specific documents and records relevant to the return under enquiry.
• Visit business premises (with notice in routine cases, without notice in serious cases).
• Issue formal information notices under Schedule 36 of the Finance Act 2008, enforceable in tribunal.
• Apply to a tribunal for an order to compel third parties (banks, letting agents, employers) to produce records.
• In serious cases, obtain warrants for unannounced searches and seizures.

What inspectors cannot do:

• Require disclosure of legally privileged communications between you and your tax adviser.
• Compel oral testimony (you are not required to be interviewed, even if requested).
• Examine documents that are not relevant to the return under enquiry.
• Pursue years that are outside the applicable time limit without making a formal discovery assessment.
• Require disclosure of medical or other genuinely private records that are not relevant to tax.

Settlement negotiations and exit routes

Most HMRC investigations end in settlement rather than tribunal. The negotiation involves four moving parts: the tax amount, the interest, the penalty band, and the time-to-pay structure. A specialist who handles HMRC settlements regularly knows the leverage on each:

1. 1On tax amount: contesting specific elements of the calculation, the basis of HMRC's estimate, or the categorisation of items as taxable.
2. 2On interest: limited room for negotiation; calculated mechanically. Some scope on the start date for accrual.
3. 3On penalty band: meaningful room for negotiation. The behaviour categorisation, the unprompted-vs-prompted status, and the quality of cooperation all affect the multiplier.
4. 4On time to pay: meaningful room for negotiation depending on the taxpayer's ability to pay and the credibility of the proposed schedule.

A well-handled settlement negotiation can reduce the total cost by 30% to 50% versus an aggressively defended position that loses at tribunal. The reverse is also true: a poorly-handled engagement can increase the position significantly. Engagement quality is what determines the outcome.