Guide
Tax investigation fees: what representation costs in 2026
Updated
Adviser fees track scope and time, and the market quotes in recognisable bands. Here is what those bands are, how the charging models differ, and where doing it yourself is a respectable answer.
The fee bands
| Work | Typical fee |
|---|---|
| Reviewing the letter and advising on a response | Often a fixed initial fee, sometimes free |
| Single-aspect enquiry, handled to closure | £500–£1,500 |
| Full enquiry into a return, handled to closure | £1,500–£5,000+ |
| COP8 / COP9 and complex cases | Substantially more, scoped per case |
Charging models vary: fixed fees for defined scopes, hourly rates for open-ended correspondence, and staged fees for long cases. Fixed fees suit aspect enquiries; for full enquiries ask what the quoted figure includes, and specifically whether meetings with HMRC and settlement negotiation are inside it. Where fee protection insurance exists, the insurer typically pays the adviser under the policy's terms, see the insurance guide.
What the fee buys
- Scope control: advisers answer what was asked and politely decline fishing expeditions, which shortens enquiries; see how long investigations take.
- Penalty positioning: penalties are behaviour-based percentages of the extra tax, from nil for reasonable care up to 100% for deliberate and concealed (higher for some offshore matters), with reductions for the quality of disclosure and cooperation (gov.uk). Presenting behaviour and disclosure well is where advisers routinely earn their fee.
- Knowing when to stop: experienced advisers settle points that should settle and contest points worth contesting, and can tell the difference.
When DIY is reasonable
A simple aspect enquiry, one or two named entries, records that support them, no behaviour question in play, can reasonably be handled yourself: respond to what is asked, by the deadline, with documents rather than argument. HMRC's compliance checks pages (gov.uk) explain the process and your rights. The honest trigger points for getting help: the enquiry widens, a meeting is proposed, penalties are mentioned, or the letter carries a COP number.
Figures are typical 2026 quotes and vary with complexity; any extra tax, interest and penalties are separate from fees and depend on the facts. Nothing here is tax advice. Get fee quotes scoped to your actual letter.