Receiving a letter from HMRC, informing you that a tax investigation has commenced is probably the one piece of correspondence we all dread. The very formal and legalistic language used in a tax investigation letter, particularly one issued by HMRC under Code of Practice 9 is worrying and intimidating. And lets be honest, that is part of HMRC’s intention.

An HMRC tax investigation letter can come in many forms, each carrying its own particular nuances. That said, basic case selection for a tax investigation is pretty much the same, regardless of size, scale or gravity. If you receive a tax investigation letter from any HMRC department then there are likely well founded reasons behind why you or your business has been selected.


Please refer to our dedicated page Why have I been selected for tax investigation? for more information. A tax investigation letter from an HMRC local compliance office will generally focus on one or more aspects of your self assessment tax return. Approximately 95% of tax investigation are launched based upon risk. HMRC’s run ongoing analyses of all self assessment tax returns. This analyses produce a risk score for each case based upon the information contained within the return, patterns and inconsistencies when compared with previously submitted returns and of course information that they may already hold. If you receive a tax investigation letter from HMRC; you can be certain of one thing. The investigator feels that tax has been underpaid.


HMRC will generally launch a compliance intervention by beginning a check of self assessment tax return. There check will usually focus on one year to begin; but invariably they will seeking to identify a loss of tax that can be scaled back to earlier years. The language in the letter may have changed; but the intention, process and legislation have not. A check of self assessment tax return will be conducted under Section 9a TMA 1970; but HMRC have an array of other powers available to them should you fail to comply.

You can read more detailed information by visiting the following pages:

Hidden Economy Teams

We are seeing many more tax investigation letters from HMRC’s Hidden Economy Teams. Hidden Economy Teams focus on individuals and businesses who may be operating outside of the tax system. They are heavily resourced and any contact from an HMRC Hidden Economy Team needs to be treated with particular respect. You can find more detailed information reading our article on HMRC Hidden Economy Teams.


If HMRC send you a tax investigation letter under the COP 9 procedures, then they suspect you of committing serious tax fraud.

Your COP 9 tax investigation letter will come from HMRC’s Fraud Investigation Service. Any letter from this team should be treated with the utmost seriousness. Immediate action is essential from the outset and all HMRC contact should be made through a tax investigation specialist. The opening approach, contact and outline disclosure sets the tone. This is not a time for mistakes or half measures. A civil case conducted being under Code of Practice 9 can quite easily aggravate and escalate into a criminal prosecution. You should seek advice from a tax investigation specialist without delay.

Further information on Code of Practice 9:

Please do take some time to read through these guides thoroughly, as COP 9 is certainly no time for half measures.


We do not charge for giving you an experienced view. However long our free tax investigation consultation takes; you can be assured of robust advice that will show you some light at the end of what may seem a very long dark tunnel. You will be getting free tax investigation advice from a former, senior HMRC tax inspector, so why not take advantage of the opportunity.

Please call us on 0330 999 5000  if you have any questions or concerns. Whatever you do, do not bury your head in the sand. Putting that tax investigation letter in the draw, in the hope that it will go away, could be costly. Be positive and proactive early – place your trust in Admiral Tax Investigations. We will not let you down.