Investigation letter · COP9 · CDF
Code of Practice 9 and the Contractual Disclosure Facility
For a letter that mentions Code of Practice 9 (COP9), the Contractual Disclosure Facility (CDF) or HMRC's Fraud Investigation Service. This page quotes HMRC's own code, word for word, with the source and the date it was last checked.
Last reviewed 8 October 2026 · How Tax Letters checks its facts
What HMRC's code says
- What it is
- Code of Practice 9 says: “This Code of Practice explains how the Fraud Investigation Service (FIS) at HM Revenue and Customs (HMRC) carries out civil investigations in cases where we suspect fraud.” [1]
- If your letter offers the Contractual Disclosure Facility
- Code of Practice 9 says: “You have 60 days from the date you receive the offer of the CDF to accept or reject it.” [1]
- On advice
- It also says: “We strongly advise that you seek independent professional advice before you respond to HMRC’s offer of the CDF.” [1]
- How Code of Practice 8 differs
- HMRC's Code of Practice 8 says it explains how the Fraud Investigation Service (FIS) at HMRC carries out civil investigations in certain cases where Code of Practice 9 is not used. [2] Code of Practice 8 investigations.
Tax Letters does not cover these investigations in detail. This page shows what HMRC's own code says, where it says it, and where to find help.
Need help with this?
You can also deal with HMRC directly, free, without any adviser. Free help: TaxAid, which says it helps “people who can’t afford to pay for help”, and Citizens Advice.
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Sources
- GOV.UK: Code of Practice 9 from 14 June 2023 (checked 8 Oct 2026)
- HMRC: Code of Practice 8 (GOV.UK PDF) (checked 8 Oct 2026)