Code of Practice 8 (COP8) and Code of Practice 9 (COP9) are both used by HMRC's Fraud Investigation Service, but they mean different things. COP8 is used where HMRC suspects a significant loss of tax, for example through bespoke avoidance, but does not suspect fraud. COP9 is used specifically where HMRC suspects tax fraud, and comes with an offer of the Contractual Disclosure Facility, which you have 60 days to accept or reject. Reading the letter carefully, and understanding which one you have, is the first thing to do.
The figures in this guide come from HMRC's published Code of Practice 9 and its COP8 guidance. For the time limits behind these letters, see HMRC's assessment time limits guidance and our guide on how far back HMRC can investigate. Correct as at 10 August 2026.
What is COP8?
COP8 is HMRC's code for civil investigations into cases where it believes there may be a significant loss of tax, but fraud is not suspected. HMRC's own guidance explains that COP8 is used to establish the facts and recover any tax, interest and penalties due, and states plainly that the investigation is "not undertaken with a view to a criminal prosecution." This is set out in HMRC's Code of Practice 8 guidance.
COP8 cases often involve complex or bespoke tax planning, structures HMRC wants to test, or self assessment enquiries HMRC's specialist teams have taken over from a local office. It covers individuals, partnerships, companies and trusts, across all the taxes HMRC administers.
Importantly, a COP8 investigation is not fixed. HMRC's guidance is explicit that if it suspects or finds evidence of fraud at any point during a COP8 investigation, it may switch to dealing with the matter under COP9 instead.
What is COP9?
COP9 is used specifically where HMRC suspects tax fraud, meaning deliberate, dishonest behaviour that has led to a loss of tax. Under COP9, HMRC offers the Contractual Disclosure Facility (CDF): if you make a complete, accurate and honest disclosure of all deliberate behaviour, HMRC commits not to pursue a criminal investigation for the fraud you disclose. This is confirmed directly in HMRC's Code of Practice 9 guidance.
You have 60 days from the date you receive the CDF offer to accept it or reject it. There is no third option: not responding within 60 days is treated as a rejection, and HMRC may then begin an investigation which could be a criminal one.
If you accept, you must disclose all deliberate behaviour and all other irregularities, attend meetings if asked, and repay the tax, interest and penalties due. Penalties in COP9 cases can exceed 200% of the tax lost before any reduction for cooperation, though the level you actually pay depends heavily on how promptly and fully you disclose.
COP8 and COP9 side by side
| Feature | COP8 | COP9 |
|---|---|---|
| What HMRC suspects | Significant tax loss, not fraud (for example, bespoke avoidance) | Deliberate tax fraud |
| Criminal prosecution | Not the intention of the investigation | Held back only if you accept and comply with the Contractual Disclosure Facility |
| Formal offer to respond to | None; you simply engage with the investigation | Contractual Disclosure Facility (CDF), with a 60-day window to accept or reject |
| Can it change to the other code | Yes, HMRC can move a COP8 case to COP9 if it finds evidence of fraud | Can escalate to a criminal investigation if the disclosure is rejected, incomplete, or found to be false |
| Assessment period if you admit deliberate behaviour | Not applicable in the same way | Up to 20 years, or longer where legislation exceptionally permits |
What should I do if I've received one of these letters?
Read the letter in full before doing anything else. It will tell you which code applies and, for COP9, will enclose the CDF offer, an acceptance letter, a rejection letter and a disclosure form.
For COP9 in particular, the 60-day clock starts from the date you receive the letter, not the date you decide to act. HMRC's own guidance strongly recommends appointing an adviser who specialises in COP9 work before you respond, because the decision to accept or reject the CDF has serious and largely irreversible consequences.
Do not sign anything, including a Certificate of Full Disclosure or a CDF rejection letter, until you and your adviser have gone through your full tax position. Signing a document you later need to walk back is far harder than taking proper advice before you sign.
Worked example
Example. Robert, a company director, receives a letter from HMRC's Fraud Investigation Service. The letter states it is issued under Code of Practice 8 and relates to a tax planning arrangement his company used three years ago. It does not mention the Contractual Disclosure Facility.
Robert checks the letter against HMRC's COP8 guidance and confirms this is not a fraud allegation: HMRC wants to test whether the arrangement worked as intended and, if not, recover any additional tax due. He appoints an adviser, cooperates with the investigation, and provides the information HMRC requests.
During the process, HMRC's officer raises a specific transaction that looks, on the facts, deliberately mis-recorded rather than simply the product of an aggressive but honest tax position. At that point HMRC tells Robert it is considering treating this part of the case under COP9 instead. This is exactly the scenario HMRC's own guidance describes: a COP8 case can move to COP9 if fraud is suspected during the investigation, and Robert now needs to take that step, and its consequences, as seriously as a case that started as COP9 from day one.
What this means in practice
Reading the letter, identifying which code applies, and pulling together your records for the years mentioned are things you can start immediately without an adviser.
Deciding how to respond, particularly for COP9, is not something to work through alone. Whether to accept or reject the CDF offer, how to frame an outline disclosure, and how your behaviour will be categorised all affect your penalty and, in the most serious cases, whether the matter stays civil or becomes criminal. Get advice before the 60-day window narrows.
If you are not sure which code your letter falls under, or whether an ongoing COP8 case is at risk of moving to COP9, our tax investigations page covers how HMRC's formal enquiry powers work more broadly, and our dedicated Code of Practice 9 page goes into the CDF process in more depth.
Frequently Asked Questions
No. COP8 is used where HMRC suspects a significant tax loss but does not, at that stage, suspect fraud. HMRC states plainly that a COP8 investigation is not undertaken with a view to criminal prosecution, though it can be reclassified to COP9 if fraud is suspected later.
If HMRC does not hear from you within 60 days, it treats this as a decision to reject the Contractual Disclosure Facility offer and may begin an investigation into the suspected fraud, which could be a criminal one.
Yes. If you genuinely believe you have not brought about a loss of tax through deliberate behaviour, you can sign the rejection letter and explain your position. HMRC says it keeps an open mind to an innocent explanation, but you should take advice before rejecting, since HMRC will then investigate on its own terms.
Accepting the CDF and admitting deliberate behaviour means HMRC can seek tax, duty, interest and penalties for up to 20 years, or longer where legislation exceptionally allows it. Our tax investigations page and our guide on how far back HMRC can go cover this in more detail.
HMRC's own guidance suggests appointing an adviser who specialises in COP9 work in addition to your regular adviser, given how much rests on the initial disclosure and the 60-day deadline. This is different from ordinary compliance work.
Talk to us before you respond
If you have received a COP8 or COP9 letter, speak to Ghulam Alahi, Managing Director, who leads our work on Code of Practice 9 and serious HMRC enquiries, before you reply to HMRC or sign anything. The first conversation is about understanding exactly which process you are in, what the letter does and does not tell you, and what your options are within the time you have. Call 020 8554 2135 or email info@visionconsulting.co.uk, or get in touch via our contact page.
By the Vision Consulting team.
This is general information, not advice. Your position depends on your circumstances.