Receiving a COP9 letter from HMRC is a serious and stressful situation. Code of Practice 9 (COP9) is issued when HMRC suspects serious tax fraud, but it also gives you a critical opportunity: to make a full, honest disclosure and avoid criminal prosecution.
However, many individuals and businesses make costly mistakes during the COP9 process — mistakes that can increase penalties or even lead to prosecution.
In this guide, we outline the top 5 COP9 disclosure mistakes and explain how to avoid them.
1. Underestimating the Seriousness of a COP9 Investigation
One of the most common and dangerous mistakes is not taking COP9 seriously enough.
A COP9 letter means HMRC already believes there has been deliberate tax behaviour. This is not a routine enquiry or compliance check.
Why this is risky:
- HMRC already has intelligence or evidence
- Any delay or casual response raises suspicion
- Incorrect handling may trigger criminal proceedings
What to do instead:
Seek specialist COP9 advice immediately. Early expert involvement protects your position and ensures all communications with HMRC are handled correctly.
2. Making an Incomplete or Partial Disclosure
A COP9 disclosure must be full, complete, and truthful. Many taxpayers try to:
- Disclose only what HMRC already knows
- Leave out offshore income or historic issues
- “Test the water” with partial information
This approach almost always backfires.
Why this is risky:
- HMRC carries out forensic reviews
- Undisclosed issues discovered later invalidate the COP9 protection
- HMRC may withdraw the offer of immunity from prosecution
What to do instead:
Ensure your disclosure covers all irregularities, including:
- Undeclared income
- Offshore assets
- VAT irregularities
- Corporation or personal tax errors
3. Missing Key Deadlines in the COP9 Process
COP9 investigations are time-critical. HMRC sets strict deadlines, including:
- 60 days to accept or reject the COP9 offer
- Timelines for submitting the Outline Disclosure
- Full Disclosure Report deadlines
Why this is risky:
- Missed deadlines signal non-cooperation
- HMRC may escalate the case
- Penalties can increase significantly
What to do instead:
Work with a professional who manages deadlines, correspondence, and submissions, ensuring nothing is missed.
4. Communicating Directly with HMRC Without Professional Support
Another major mistake is responding directly to HMRC without specialist representation.
COP9 cases involve:
- Technical tax law
- Legal privilege
- Negotiation with HMRC Fraud Investigation Service (FIS)
Why this is risky:
- Innocent statements can be misinterpreted
- You may unintentionally admit deliberate behaviour
- Lack of legal privilege exposes sensitive information
What to do instead:
Use a COP9 specialist advisor who understands HMRC’s approach and protects your legal position throughout the investigation.
5. Failing to Prepare a Proper Disclosure Report
The Disclosure Report is the most important document in a COP9 case. Poorly prepared reports often:
- Lack supporting evidence
- Contain inconsistencies
- Fail to explain behaviour clearly
Why this is risky:
- HMRC may challenge figures aggressively
- Negotiations become prolonged
- Final settlements may be higher than necessary
What to do instead:
A strong disclosure should include:
- Clear explanations of irregularities
- Accurate calculations
- Supporting documents
- A well-reasoned narrative
Why Expert COP9 Advice Matters
A COP9 investigation is not just about numbers — it’s about protecting your freedom, reputation, and finances.
With the right professional support, you can:
Achieve the best possible outcome
Avoid criminal prosecution
Reduce penalties
Resolve the matter efficiently
