Compliance check vs full investigation: what's the difference?

"Compliance check" is the umbrella term

A compliance check is HMRC's catch-all for looking into your tax affairs, using their statutory information powers. It can be entirely routine, HMRC profile cash-heavy trades, and being selected does not mean you have done anything wrong. What matters is how it is handled.

Aspect check vs full enquiry

An aspect check looks at one specific thing, a single expense category, or one figure that does not add up. A full enquiry examines your entire return.

An aspect check can widen into a full enquiry if the answers raise more questions. That is exactly why early, careful handling matters: a tidy response to a narrow question stops it spreading.

COP8, suspected avoidance, not fraud

Code of Practice 8 is used when HMRC want to investigate a significant amount of tax but do not suspect fraud, often where a tax-avoidance arrangement is involved. It is serious and thorough, but it is not a fraud investigation.

COP9, suspected serious, deliberate fraud

Code of Practice 9 is the most serious civil investigation HMRC run. It is opened when they suspect deliberate conduct that brought about a loss of tax. It comes with the Contractual Disclosure Facility and strict deadlines, and it carries real risk, including criminal prosecution if it is mishandled.

If you have received a COP9 letter, do not respond without specialist representation.

What HMRC can ask for

Using their information powers, HMRC can ask to see records that are reasonably required to check your position: bank statements, invoices, mileage logs, contracts and more. But "reasonably required" has limits. You do not have to empty every drawer, and you can push back on requests that overreach. Knowing what is fair game, and what is not, is half the battle.

How far back HMRC can go

The window depends on behaviour. For an innocent mistake, HMRC can normally go back four years. For carelessness, six. For deliberate behaviour, up to twenty years. The further back they can reach, the more is at stake, which is why how a check is framed at the very start matters so much.

Why the difference matters

The right response to a routine aspect check would be completely wrong for a COP9, and the other way round. Reading the situation correctly, and responding in the right register, is the difference between a check that closes quietly and one that spirals. That is the part we handle for you.