• Home
  • >
  • Blogs
  • >
  • Understanding Code of Practice 8 (COP 8) Investigations: When HMRC Comes Knocking

Understanding Code of Practice 8 (COP 8) Investigations: When HMRC Comes Knocking

Published By Aayush Niraula
Published Date: August 7, 2025
Categories: Code of Practice 8

( Last Updated: August 16, 2025 )

Are you facing the daunting prospect of an HMRC investigation? Has a letter referencing "Code of Practice 8" landed on your doormat? This isn't just a routine query; it's a serious signal that HMRC's specialist Fraud Investigation Service (FIS) suspects significant tax underpayments.

Understanding COP8 is crucial, as is knowing how to respond effectively. This in-depth guide will explore the complexities of COP8, what it is, why you might be targeted, how it works in practice, the possible consequences and most importantly, what to do if HMRC comes knocking?

The Unseen Threat: What is a Code of Practice 8 Investigation?

A Code of Practice 8 investigation is a formal civil inquiry by HMRC's Fraud Investigation Service. It is used when HMRC suspects a significant loss of tax due to aggressive or complex tax avoidance arrangements but lacks direct evidence of fraud.

Characteristics of a COP8 Investigation

  • Civil, Not Criminal (Initially)
    Although serious, it is usually a civil inquiry where HMRC aims to recover unpaid tax, interest, and penalties rather than pursue criminal charges. However, if deliberate fraud is discovered during a COP8 investigation, it can be escalated to a more serious Code of Practice 9 (COP9) inquiry, which may involve criminal prosecution.
  • No initial fraud Allegations
    When HMRC issues a COP 8 or a Requirement to Correct, it is important to note that, at the time of issuance, HMRC does not necessarily suspect that the individual has intentionally engaged in illegal activities to reduce their tax liability (such as tax fraud or tax evasion).

How does HMRC gather information for COP8 investigations?

HMRC’s ability to identify cases for COP8 investigations relies on advanced data analytics. They continuously collect and analyse extensive data from various domestic and international sources, enabling them to pinpoint potential tax underpayments linked to complex or high-risk arrangements. This includes data reported directly by taxpayers through self-assessment tax returns and real-time payroll submissions from employers.

HMRC’s primary sources of intelligence include information received directly from UK financial institutions such as banks, as well as key government registers like Companies House and the Land Registry. In addition, international information-sharing agreements like the Common Reporting Standard (CRS) allows HMRC to access comprehensive details on offshore accounts and foreign investments.,

Furthermore, HMRC often acts on information reported by whistleblowers or anonymous informants, which can trigger initial scrutiny.

Key Common Triggers That Often Lead to a Code of Practice 8 Investigation:

  • Significant Discrepancies: When HMRC’s data does not align with a taxpayer’s declared income or gains, raising suspicions of underreporting.
  • Complex Financial Structures: The use of trusts, offshore companies, or other complicated investment vehicles designed to obscure true tax liabilities.
  • Large or Unusual Overseas Transactions: Significant movements of funds or assets with foreign connections that require further scrutiny.
  • Lifestyle and Wealth Inconsistencies: Situations where an individual’s declared income appears insufficient to support their apparent lifestyle or asset holdings.

What to do If you have received a COP8 letter from HMRC?

It is essential not to ignore a COP8 letter, as this can lead to a more serious investigation and significantly higher penalties. Additionally, destroying, altering, or providing false information is a criminal offence that will severely damage your position.

What to do If you have received a COP8 letter from HMRC - code of practice 8

Your first step should be to consult a qualified tax advisor who can formally acknowledge the letter on your behalf, allowing you time to prepare a well-considered response and effectively manage the investigation.

At UK Property Accountants, with many years of experience in handling such cases, we are well-equipped to guide you through every stage of the process, providing expert support to safeguard your interests.

The Code of Practice 8 Investigation Process

HMRC has published a statement which outlines the common steps in COP8 Investigation process:

Opening the Enquiry: The Initial Notification

The investigation officially begins when you receive a formal letter from HMRC. This letter will clearly state that a COP8 enquiry has been opened into your tax affairs and will generally outline the scope of their investigation. It will also typically include an initial request for specific information and documents that HMRC believes are relevant to their concerns.

The COP8 letter will usually specify which tax years and issues that are under scrutiny.

Gathering Information

Once a Code of Practice 8 enquiry is opened, HMRC will scrutinise your tax affairs using the information you provide alongside extensive data from various sources discussed above such as CRS, Companies House, etc.

During this stage, HMRC may:

  • Issue further information requests: They may come back to you several times to ask for more documents or to clarify elements they are unsure of.
  • Investigate historical periods: Depending on the severity of the suspected tax loss, HMRC can investigate back 4-6 years usually, but potentially up to 20 years if they suspect deliberate behaviour, or even longer in some cases involving offshore matters.
  • Request meetings and/or interviews: While these are not interviews under caution (as would be the case in a criminal investigation), they are critical opportunities for HMRC to gather more context and ask questions.

Note


Providing false, misleading or incomplete information during a COP8 investigation will be considered as a criminal offence and may lead to HMRC conducting a criminal investigation leading to prosecution.

Outcome

HMRC will decide the outcome of a Code of Practice 8 investigation based on the evidence collected and any negotiations that occur. There are several potential outcomes:

No Further Action (NFA)

This happens if HMRC is satisfied that your tax affairs are fully compliant or if you provide adequate explanations and evidence showing no tax underpayment. In such cases, the investigation closes with no penalties or additional action.

Tax, Interest and Penalties

HMRC identifies underpaid tax, you will be liable for the outstanding tax amount, along with interest and potential penalties. The level of penalties depends on the nature of the behaviour leading to the underpayment.

Penalties can be reduced for positive behaviour. When determining penalty HMRC considers behaviours such as:

  • how and when you tell HMRC about any offence
  • how and when you co-operate with HMRC during the investigation

Penalties can range from 0% for genuine errors made without prompting, to 100% or more for deliberate actions. In particularly serious offshore cases, penalties can reach 200%.

For more information regarding the penalties, please refer to our article ‘HMRC Nudge Letters & WDF: Declare Offshore Income

Escalation to COP9

When HMRC finds evidence of deliberate fraud during a COP8 investigation, they may escalate the case to a more serious Code of Practice 9 (COP9) investigation. Under COP9, HMRC offers the taxpayer the chance to make a full and honest disclosure of all tax irregularities through a process called the Contractual Disclosure Facility (CDF). By agreeing to this, the taxpayer admits to the deliberate wrongdoing but, in return, HMRC agrees not to pursue criminal prosecution. If the taxpayer refuses or fails to make a complete disclosure under the CDF, HMRC may initiate a full criminal investigation.

Appeals

If you are unhappy with HMRC's final decision or the proposed settlement, you have the right to appeal within 30 days of the decision. There are two main avenues:

  • Internal Review: You can request an internal review by HMRC. This involves a different HMRC officer, independent of the original investigation, reviewing the decision. This process aims to provide a fresh perspective and can sometimes lead to a resolution without needing to proceed to a tribunal.
  • Tax Tribunal: If the internal review does not yield a satisfactory outcome, or if you choose to bypass it, you can take your appeal to the First-tier Tax Tribunal. This is an independent judicial body that will hear your case and make a binding decision.

Conclusion

A COP8 investigation is a serious civil inquiry conducted by HMRC’s Fraud Investigation Service when there is suspicion of significant tax underpayment through complex arrangements, but without initial fraud allegations. It involves detailed scrutiny of your tax affairs, potentially covering many years, and can lead to the recovery of unpaid tax, interest, and substantial penalties. Although COP8 investigations focus on factual assessment and civil remedies, they can escalate to a criminal Code of Practice 9 (COP9) inquiry if deliberate fraud is uncovered. It is crucial to respond promptly and seek expert advice to manage the process effectively and protect your interests.

Need Help?

Need more info on Code of Practice 8 (COP 8) Investigations?

Aayush Niraula
Our Complete Guides
File your self assessment
Related Posts

Introducing RentalBux: Our MTD Software for Landlords

Generic software doesn't understand property businesses and require manual intervention to meet deadlines. That's why we developed RentalBux!

  • Built by Property Experts
  • Designed for UK Landlords
  • HMRC Recognised and MTD Compliant

Confused where to start?

Schedule a Free 15-minute discovery call by providing your contact details, mentioning your requirements, and selecting a convenient date for the call.

How our discovery call works:

Please wait while the page is loading
Current Progress
Current Progress

Complete Our Contact Form

Discovery Calls Scheduled

Receive a Tailored Proposal

Success message!
Warning message!
Error message!