by Asim Abbas
11 November 2026 
HMRC compliance checks: what to do if HMRC opens an enquiry
HMRC compliance checks: what to do if HMRC opens an enquiry
A letter from HMRC saying it’s checking your tax return can be worrying, but most compliance checks are routine and many end with no change.
- HMRC can open an enquiry within 12 months of filing
- Checks can cover one aspect or the full return
- Penalties depend on behaviour and disclosure
- Get professional help before replying
How you respond matters: clear, accurate answers on time usually lead to a quicker outcome and lower penalties if anything is wrong.
This guide explains the types of check, time limits and how to handle the process.
Types of HMRC check
| Type | What it involves |
|---|---|
| Aspect enquiry | A specific item, such as expenses or a property sale |
| Full enquiry | The whole return and underlying records |
| Nudge letter | A prompt to check your return, often from data HMRC holds |
| Employer or VAT check | Records, systems and returns for a business tax |
Time limits
HMRC can usually open an enquiry into a Self Assessment return within 12 months of the date it was filed. After that, HMRC needs a discovery assessment, which can go back four years for innocent errors, six for careless and 20 for deliberate behaviour.
Late tax return penalty calculator
Penalty and interest exposure.
Why you might be checked
- Figures out of line with similar businesses
- Large or unusual expense claims
- Data from banks, platforms, letting agents or overseas authorities
- Big changes from one year to the next
- Random selection
How to respond
- Read the letter carefully and note the deadline
- Tell your accountant immediately
- Provide only the information requested
- Ask for more time if you need it
- Answer honestly and don’t guess
A sole trader claims £6,500 for a home office. HMRC opens an aspect enquiry. Her accountant shows the calculation was based on the whole house rather than the business-use proportion. The correct claim is £1,300. She pays the extra tax and interest, and because she helped fully and the error was careless, the penalty is reduced to the minimum.
Fixed-fee accountancy support
Transparent monthly packages for sole traders, landlords and limited companies. Fixed fees agreed upfront, VAT included.
Get a fixed-fee quoteCall 0161 531 4179Penalties for inaccuracies
| Behaviour | Unprompted | Prompted |
|---|---|---|
| Careless | 0% to 30% | 15% to 30% |
| Deliberate | 20% to 70% | 35% to 70% |
| Deliberate and concealed | 30% to 100% | 50% to 100% |
Penalties are lower when you tell HMRC about errors, help it work out the tax and give access to records. If you took reasonable care, no penalty applies.
How checks end
HMRC issues a closure notice with its conclusions. If you disagree, you can ask for an internal review or appeal to the tax tribunal. Fee protection insurance can cover accountancy costs for enquiries.
Read HMRC’s compliance checks guidance, see our voluntary disclosure guide, or ask our tax investigations team to handle HMRC for you.
What should I do next?
Note the deadline.
For the item queried.
Controlled and accurate.
Frequently Asked Questions
How long does an HMRC enquiry take?
Simple aspect enquiries can close in a few months. Full enquiries can take a year or more.
How far back can HMRC check?
Four years for innocent errors, six for careless and 20 for deliberate behaviour.
Will I get a penalty?
Only if there’s an inaccuracy and you didn’t take reasonable care. Cooperation reduces penalties.
Can my accountant deal with HMRC?
Yes. An authorised agent can handle all correspondence.
What is a nudge letter?
A letter asking you to check your return, usually based on data HMRC has received.
Need help with this? Wingate Accountants offers fixed-fee online accountancy support across the UK. Call 0161 531 4179 or request a quote at wingateaccountants.co.uk.
About the Author
Stephen Reynold
I’m Stephen Reynold, an accountant at Wingate Accountants. I work with sole traders and small companies, turning tax rules into clear, practical next steps.
