What triggers an HMRC enquiry
Just as HMRC use a variety of sources to identify the cases they investigate, there are numerous reasons why taxpayers may find themselves subject to an HMRC enquiry.
Understanding what triggers risk flags for HMRC – within a broader awareness of the enquiry process – will help you to think about your risk, and to be prepared for the pressures that come with an HMRC investigation.
Common HMRC triggers you should be aware of
Tax return behaviour
Errors, omissions or non-compliant behaviour that can trigger an enquiry include:
- Late filing of returns – self-assessment, corporation tax (CT), VAT, PAYE
- Late or missing payments
- Repeatedly amended returns – this could indicate weak record-keeping
- Obvious arithmetic errors or figures that seem wrong on the face of the return
- Returns showing a small tax liability against a high turnover (or vice versa)
Inconsistencies across your tax filings
HMRC’s systems automatically cross-check the different returns a taxpayer submits.
Any discrepancies identified are an obvious trigger for HMRC. Examples of discrepancies include:
- Turnover in your business accounts not reconciling with the turnover in your tax return
- Inconsistent PAYE/RTI data when compared with declared staff costs or directors’ remuneration
- CIS returns not aligning with the declared position of subcontractors and/or contractors
- Large or repeated VAT repayment claims without obvious commercial support
Discrepancies with third party data
HMRC’s Connect system will cross-reference your return against external data sources. Inconsistencies that would catch HMRC’s attention may involve:
- Bank interest – what’s declared on tax return is lower than figures reported to HMRC by UK banks
- Rental income– absent or low compared with data obtained from Land Registry and council tax records
- Employment income – not matching the PAYE records
- Online platforms – income is either not declared or under-reported when compared to information received from digital platform reporting .Examples include eBay, Vinted, Airbnb, Etsy and Just Eat
- Overseas income, dividends and account balances – inconsistent with data received under the Common Reporting Standard (CRS)
- Payment providers–receipts that were not reported as turnover in accounts or tax returns. Examples include PayPal and Stripe
Year-on-year swings and loss patterns
Sharp movements in your profits, losses, turnover or expenditure without an evident cause would attract HMRC attention even though there may be a legitimate commercial explanation. Examples include:
- Turnover or profit falling suddenly
- Repeated losses – particularly where the business continues to fund the business owner’s lifestyle
- Expenses rising sharply without a matching increase in turnover
Large or unusual one-off transactions
- Standalone events can trigger an HMRC investigation even where your broader return looks fine. For example:
- Property disposals giving rise to tax liabilities – capital gains tax (CGT), annual tax on enveloped dwellings (ATED), stamp duty land tax (SDLT)
- Share disposals and business sales
- Director loan account movements which could create S455 or benefit-in-kind issues
- Major one-off expense claims or capital allowance claims
Lifestyle v declared income
Connect uses third-party data to build a lifestyle picture and compares this against declared income. Mismatches that could prompt an enquiry include:
- Significant deposits or transfers inconsistent with declared income stream.
- Property purchases, vehicles, school fees, or social media activity inconsistent with reported earnings.
Figures out of line with industry benchmarks
HMRC compare your reported margins, expenses and ratios with other businesses in the same sector. Differences flagged for HMRC’s attention include:
- Gross or net profit margins materially below industry average
- Expense ratios unusually high for the trade
- Large or unusual expense claims that look disproportionate to turnover
Tax avoidance schemes
Taxpayers using tax avoidance schemes or complex structures can come under scrutiny from HMRC. For example:
- Use of disclosed (or undisclosed) tax avoidance schemes under the DOTAS and DASVOIT disclosure regimes
- Offshore structures, trusts or arrangements inconsistent with your declared income
- Aggressive remuneration planning – loan schemes, contractor arrangements etc
Linked enquiries
It’s not uncommon for one HMRC enquiry to trigger others, such as:
- Directors of a company that’s already under investigation
- Companies in the same group as a company that’s already under investigation
- An enquiry into one taxpayer raising possible issues with a taxpayer not directly linked e.g. a supplier
Staying ahead of HMRC enquiry triggers
Almost every trigger is driven by data mismatch, be it an internal mismatch between a taxpayers’ own returns or an external mismatch against information provided to HMRC.
As the vast majority of tax investigation selections are now algorithmically driven by Connect’s data-matching, the most effective defensive strategy is pre-submission reconciliation.
To minimise your risk of an HMRC enquiry, we recommend these steps:
- Carefully reconcileall tax returns and accounts prior to submission – personal tax return, CT return, VAT return, PAYE/CIS returns, company accounts
- Pre-empt third-party data–check what banks, online platforms, Land Registry and overseas financial institutions will have reported
- Document any one-off transactions and unusual swings – contemporaneously, with a one-page rationale on file with supporting evidence
- Make a white space disclosure – use the ‘any other information’ box on the tax return where a figure could look anomalous, as this explanation often deters Connect-driven enquiries
How BKL can help
Our Tax Risk & Dispute Resolution team have a strong understanding of the underlying risks that HMRC are trying to address through their investigations.
We can help you to proactively manage your risk of triggering an enquiry, narrow the scope of enquiries and progress matters to conclusion as quickly as possible.
To discuss your situation in confidence, please get in touch with your usual BKL contact or Piyush Patel using the form below.
An understanding of what is likely to prompt an enquiry is complemented by understanding how HMRC select enquiry cases.
Our Experts
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Frequently asked questions: common triggers for HMRC enquiries
How can I reduce the risk of triggering an HMRC enquiry?
The best way to reduce enquiry risk is to ensure your tax returns, accounts and supporting records are consistent, accurate and supported by evidence.
Many HMRC enquiries begin because of data mismatches rather than suspected wrongdoing. Before submitting returns, businesses and individuals should reconcile information across corporation tax, VAT, PAYE, CIS and self-assessment filings, while keeping clear records of significant transactions, unusual figures and tax positions.
What is HMRC Connect and why does it matter?
HMRC Connect is a data analysis system that compares tax return information with data from multiple internal and external sources.
The system helps HMRC identify potential compliance risks by spotting inconsistencies, unusual patterns and undeclared income. Connect can cross-reference information from banks, online platforms, payment providers, Companies House, Land Registry records and overseas tax authorities. As a result, taxpayers should assume that HMRC has access to far more information than appears on a tax return alone.
Can a legitimate drop in profits trigger an HMRC enquiry?
Yes. A significant fall in profits, turnover or tax liabilities can attract HMRC’s attention even when there is a genuine commercial reason.
HMRC’s systems are designed to identify changes that appear unusual compared with previous years or industry norms. Businesses experiencing major changes should ensure they retain evidence explaining what happened, such as economic conditions, investment activity, restructuring, loss of contracts or exceptional costs. Clear documentation can be valuable if questions arise later.
Does making a loss automatically make a business high risk for HMRC?
No. Many genuine businesses make losses, particularly during startup periods, investment phases or economic downturns.
However, repeated losses over several years may attract attention if they appear inconsistent with continued trading activity or a business owner’s lifestyle. HMRC may want to understand how the business is being funded and whether losses have been calculated correctly. Accurate records and a clear commercial rationale are important in these situations.
Why do HMRC compare businesses with others in the same industry?
HMRC use industry benchmarking to identify businesses whose financial results differ significantly from sector norms.
Being different does not mean a business has done anything wrong. Profit margins, expense levels and business models vary for legitimate reasons. However, unusually low profits, high expenses or atypical financial ratios may prompt HMRC to seek further information. Businesses should be ready to explain why their circumstances differ from the industry average.
What happens if HMRC think my lifestyle does not match my declared income?
A significant mismatch between lifestyle indicators and declared income can become a risk factor for investigation.
HMRC may compare reported income with information relating to property ownership, vehicle purchases, investments, school fees or other indicators of financial activity. This does not mean that every high-value transaction creates an enquiry risk, but taxpayers should be able to demonstrate the source of funds used for major purchases and explain any apparent inconsistencies.
Are property transactions more likely to attract HMRC scrutiny?
Yes. Property transactions often involve multiple taxes and reporting obligations, making them an area of regular HMRC focus.
Issues can arise around capital gains tax (CGT), stamp duty land tax (SDLT), annual tax on enveloped dwellings (ATED), rental income reporting and property ownership structures.
Property investors, landlords and developers should ensure transactions are reported correctly and that deadlines are met, particularly where gains, losses or relief claims are involved.
Can HMRC investigate historic tax returns?
Yes. HMRC can review earlier tax years if they believe there may have been an error, careless behaviour or deliberate non-compliance.
The period HMRC can look back depends on the circumstances and the nature of the issue being investigated. This means businesses and individuals should retain appropriate records and supporting evidence even after a tax return has been submitted. Good record-keeping can significantly reduce the difficulty and cost of responding to enquiries.
Is it true that only tax avoidance schemes trigger HMRC investigations?
No. This is a common misconception.
While tax avoidance arrangements often receive enhanced scrutiny, many HMRC enquiries relate to routine compliance issues such as reporting errors, data mismatches, undeclared income, unusual claims or inconsistencies between different sources of information. Most enquiries arise because HMRC believe there is a risk worth checking, not because it has already concluded that deliberate avoidance or evasion has taken place.
Should I explain unusual figures on my tax return?
Often, yes. Providing context for unusual figures can sometimes reduce the likelihood of unnecessary questions from HMRC.
Where a transaction, claim or financial result could appear unusual when viewed in isolation, it may be appropriate to include an explanation within the return or maintain contemporaneous documentation supporting the position taken. This can be particularly helpful for one-off transactions, significant fluctuations in performance, large relief claims or complex commercial events.
If you are uncertain about the best approach, professional advice can help you assess your risks and disclosure options.
What should I do if I am concerned that HMRC may investigate me?
The best approach is to review any potential risk areas before HMRC contact you. Early action can often reduce disruption and help resolve issues more efficiently.
This may involve checking that tax returns are accurate, ensuring supporting records are complete, reviewing historic claims or disclosures, and obtaining professional advice where a tax position may be uncertain. Businesses and individuals who understand their risk profile are generally better placed to manage an enquiry if one arises.
