How to handle an HMRC tax investigation
A plain-English guide to what an HMRC tax investigation is, what happens, and what to do next.
Written by Naomi Lai— Small business & finance writer. Read Naomi's full bio
Published Wednesday 23 September 2026
Table of contents
Key takeaways
- An HMRC tax investigation, officially a compliance check, is HMRC checking you've paid the right amount of tax and doesn't mean you've done anything wrong.
- Checks range from a quick look at one item to a full review of your accounts, and most begin with a letter that gives you a deadline to reply.
- Keeping accurate, up-to-date records and filing on time are the best ways to lower your risk and settle any check quickly.
- You have clear rights during a check, including the right to a representative, to appeal a decision, and to ask HMRC to stop the check.
What is an HMRC tax investigation?
An HMRC tax investigation is His Majesty’s Revenue and Customs checking that you've paid the right amount of tax. It's officially called a compliance check, and it isn't an accusation. Many checks are routine, and some businesses are picked at random.
During an HMRC compliance check, HMRC can look at a range of records to confirm your figures add up. These include your Self Assessment tax return, Company Tax Returns, PAYE records, VAT, and your accounts and tax calculations. HMRC will let you know about a check in writing or by phone, as explained in the GOV.UK guidance on tax compliance checks.
A check can be quick and specific, or it can be broader. Either way, the aim is to make sure the amount of tax paid matches what you actually owe.
What are the different types of HMRC investigation?
Not every check is the same, and the type you face affects how much HMRC looks at and how long it takes. Understanding the differences helps you gauge the scale of what's involved.
There are three main types of HMRC investigation:
- Aspect enquiry: HMRC checks one specific item on your return, such as a single expense or figure, and this often takes a few months
- Full enquiry: HMRC reviews your whole return or accounts in detail, which is more involved and takes longer
- Random check: HMRC selects your records at random, without any specific concern about your figures
What triggers an HMRC tax investigation?
Some checks are prompted by something specific in your records, while others are simply random. Knowing the common triggers helps you spot and fix issues before they draw attention.
Common triggers for an HMRC tax investigation include:
- inconsistencies or errors on your tax returns
- late returns, or returns that you amend repeatedly
- income that doesn't match your lifestyle
- profit that's unusually low for your sector
- large bank deposits you can't easily explain
- tip-offs, or working in a sector HMRC is currently targeting
HMRC also uses a data-matching system called the Protect Connect Programme, which compares information from banks, other government departments, and online platforms to flag figures that look out of place. Even with these triggers, some checks happen purely at random, so being selected doesn't always mean HMRC has a concern.
How likely are you to be investigated?
For most small business owners, a full investigation is uncommon, and it helps to keep the risk in perspective. HMRC can't check every taxpayer, so it focuses on returns that show red flags alongside a portion selected at random.
Your risk rises when your records contain the triggers above, such as errors, late filing, or figures that don't add up. It falls when your returns are accurate, filed on time, and backed by clear records. In short, good habits are the strongest protection you have.
What happens during an HMRC tax investigation?
An HMRC tax investigation follows a broadly predictable path, so you can prepare for each stage. HMRC keeps you informed in writing as things progress and you can bring in a representative at any point.
- Notification: HMRC contacts you in writing or by phone to tell you a check is starting and what it covers.
- Information request: HMRC asks for specific records, such as bank statements, invoices, or receipts, to support your figures.
- Review: HMRC examines your records and cross-checks them against the information it already holds.
- Meeting or visit: HMRC may ask to visit your home, business, or adviser's office, or ask you to visit them. You can have a representative present.
- Decision: HMRC writes to you with the result of the check once its review is complete.
- Settle or appeal: You pay any tax owed, or you challenge the decision if you disagree with it.
How long does an HMRC investigation take?
How long an HMRC investigation takes depends mainly on the type of check and how complex your affairs are and how information is exchanged. A quick, focused check will be over far sooner than a full review of your accounts.
As a rough guide, an aspect enquiry into a single item is usually the quickest to resolve, while a full enquiry into your whole return or accounts is more thorough and can take considerably longer. Responding promptly and keeping your records organised is the surest way to help a check reach its conclusion faster.
What to do when you receive an HMRC enquiry letter
Opening an HMRC enquiry letter can be unsettling, but a calm, methodical response makes the whole process easier. The letter sets out what HMRC is checking and what it needs from you, so it pays to keep your business records organised and to hand.
- Read the letter closely. Note any deadline, as you usually have a set period to respond.
- Check what's under review. Confirm which tax period and which items HMRC is asking about, so you know exactly what's involved.
- Gather your records. Pull together the relevant bank statements, invoices, and receipts for the period in question.
- Don't ignore the letter. Missing a deadline can lead to penalties, so respond even if you need more time.
- Consider professional advice. Speaking to an accountant or tax adviser can help, especially for a full enquiry.
- Respond within the deadline. Answer only what HMRC has actually asked, clearly and on time.
- Keep copies of everything. Hold on to everything you send and receive so you have a clear record of the check.
Penalties, interest, and your rights
If a check finds you've underpaid tax, HMRC will write to you with the result, and you'll usually have 30 days to pay any extra tax, normally with interest running from the original due date. Penalties can also apply, and how much you pay depends on your behaviour.
Penalties for inaccuracies scale according to whether you took reasonable care, were careless, were deliberate, or were deliberate and concealed. HMRC can also charge penalties if you fail to provide information or refuse a visit, though reasonable excuses, such as serious illness or bereavement, may be accepted.
How far back HMRC can go depends on your behaviour too. The assessment time limits, each running from the end of the relevant tax period, are:
- 4 years for most cases where reasonable care was taken
- 6 years where the underpayment was down to careless behaviour
- 12 years where the matter involves offshore income or gains
- 20 years where the behaviour was deliberate
You also have clear rights throughout a check. You can authorise a representative in writing to deal with HMRC on your behalf, apply for alternative dispute resolution (ADR) if you reach a deadlock, appeal a decision you disagree with, and ask HMRC to stop the check by writing to the office that contacted you.
How to reduce the risk of an HMRC investigation
You can't rule out a random check, but you can make your affairs far less likely to raise concern. Strong, consistent record-keeping is the foundation, and it also makes any check quick to resolve.
To lower your risk of an HMRC tax investigation:
- Keep accurate, complete records of your income and expenses throughout the year.
- File your returns and pay your tax on time, every time.
- Reconcile your accounts regularly so errors surface early, which is easier with good bank reconciliation habits.
- Explain any unusual items, such as large deposits, before HMRC has to ask.
- Use reliable software to cut down on manual errors.
Filing correctly also matters if you're registered for VAT, since the GOV.UK rules on Making Tax Digital for VAT require digital records and returns for VAT-registered businesses.
Stay investigation-ready with Xero
Being ready for a check comes down to one thing: accurate, up-to-date records you can produce at a moment's notice. Xero brings your invoices, bank transactions, and receipts together in one place, so it's easier to keep your figures reconciled and ready to explain if HMRC ever asks.
FAQs on HMRC tax investigations
These quick answers cover the questions small business owners ask most often about HMRC checks.
Do HMRC tell you if they are investigating you?
Yes. HMRC contacts you in writing or by phone to let you know a compliance check is starting and what it covers, so you'll never be investigated without being told.
What triggers an HMRC compliance check?
Common triggers include errors or inconsistencies on returns, late or repeatedly amended returns, and figures flagged by HMRC's Connect data-matching system. Some checks are also selected at random.
Can you be investigated after you've paid your tax?
Yes. HMRC can open a check after you've filed and paid, within the assessment time limits, which is why keeping your records for several years matters.
What is HMRC tax investigation insurance?
It's cover, sometimes called fee protection, that pays the professional fees of an accountant or adviser representing you during a check. It doesn't pay any tax or penalties you owe.
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