For individuals and businesses who suspect there may be gaps or errors in their historic tax affairs, the question that matters most is often ‘How far back can HMRC go for underpaid tax?’
The answer turns almost entirely on how HMRC classifies the nature of the conduct involved, and getting that classification right, or challenging it when it is wrong, can make an enormous difference to the scale of any liability.
For a confidential free discussion, call us today on 01908 538292, alternatively email us at Hello@altion-law.co.uk or complete our Free Enquiry Form and we will call you back.
What triggers an HMRC investigation?
HMRC does not generally investigate taxpayers at random. Enquiries are typically prompted by discrepancies in submitted returns, data matching against third-party records such as bank statements, land registry data, or employer payroll reporting, anonymous tip-offs, missed filing or payment deadlines, or a routine compliance review. Businesses operating in sectors that HMRC regards as carrying a higher risk of non-compliance are also more likely to be selected.
The initial window for HMRC to open a formal enquiry is 12 months from the date a tax return is filed. Where HMRC misses that window without justification, its ability to investigate using standard enquiry powers may be significantly curtailed. Exceptions exist, most notably where a taxpayer deliberately concealed information that an HMRC officer could not reasonably have identified within the standard timeframe, but those exceptions are not unlimited and they can be challenged.
If you have received any communication from HMRC indicating that your returns are under review, we can advise you from the outset on how to respond, what documentation to locate, and how to engage with the process in a way that protects your position.
How far back can HMRC go?
Once an enquiry is open, HMRC may seek to examine historical tax and financial information through a mechanism known as a discovery assessment. The time limits governing those assessments are set by statute, and they are not uniform across all circumstances.
The baseline is four years from the end of the relevant tax year. Where a taxpayer made a genuine, innocent error and took reasonable care when completing their return, HMRC’s discovery assessment powers are confined to that four-year window. This applies across most taxes, including income tax, capital gains tax, and corporation tax.
Where HMRC concludes that an error was the product of careless behaviour, broadly defined as a failure to take reasonable care, the window extends to six years. VAT is treated somewhat differently in this respect: even where carelessness is alleged, the time limit for VAT assessments remains four years. That distinction matters for businesses whose exposure spans both income tax and VAT liabilities across different periods.
Offshore matters attract a longer reach. Where anomalies involve offshore income, overseas assets, or offshore transfers, HMRC can look back 12 years, regardless of whether the underlying conduct was careless or innocent. This reflects the genuine difficulty HMRC faces in gathering information from foreign financial institutions and has been a sustained feature of its international compliance work.
At the most serious end, where HMRC believes that tax was knowingly underpaid, that records were falsified, that income was deliberately concealed, or that a taxpayer failed to notify HMRC of a taxable source of income without reasonable excuse, the time limit extends to 20 years. In practice, that can reach back to the early years of a business or to the start of a self-employed career entirely.
Why behaviour classification is so consequential
HMRC’s categorisation of a taxpayer’s conduct determines both how far back the investigation can reach and the level of penalties that follow.
For careless behaviour, penalties are typically up to 30% of the underpaid tax. Where conduct is classified as deliberate, that figure rises to 70%. Where deliberate behaviour was also actively concealed, penalties can reach 100% of the total amount owed. The financial gap between those three categories is substantial, and disputing HMRC’s classification is often the most effective way of limiting overall exposure.
The burden of proving the category of behaviour sits with HMRC, not with the taxpayer. HMRC must demonstrate on the balance of probabilities that conduct was careless and must meet a higher evidential standard if it alleges deliberate action. Tribunals have repeatedly held that inferring deliberate conduct simply from the size of an error or the perceived sophistication of a taxpayer is not sufficient to meet that test.
Our solicitors and barristers work with clients to examine the evidence relied upon by HMRC in support of its behaviour classification. Where that evidence does not reach the required standard, we challenge it. A successful challenge can reduce a finding from deliberate to careless, cutting years off the assessment period and reducing the penalty base significantly.
What HMRC can recover
Where HMRC issues a valid discovery assessment, it can seek to recover unpaid tax for the full period covered. In a deliberate conduct case, that can mean up to 20 years of outstanding liability, with statutory interest added on top. HMRC must, however, assess the position according to the law as it stood at the time of the relevant conduct, not by current standards. Where legislation has changed materially over a 20-year period, that rule can have a direct bearing on the amount actually owed.
Why choose us?
At Altion Law, our team combines the skills of solicitors and barristers with direct commercial experience, giving us a grounded understanding of what is at stake for businesses and individuals when HMRC investigates. Whether you have received a formal enquiry notice, are considering making a voluntary disclosure, or need to assess whether an existing assessment falls within HMRC’s legal powers, contact our team for clear advice on where you stand.
For a confidential free discussion, call us today on 01908 538292, alternatively email us at Hello@altion-law.co.uk or complete our Free Enquiry Form and we will call you back.
