Answers · UK 2025/26
How far back can HMRC investigate UK tax returns?
HMRC can normally re-open the last 4 tax years. With careless errors, the window extends to 6 years. For deliberate evasion or undisclosed offshore income, HMRC can go back 20 years. Always keep records for at least 5 years past the 31 January deadline.
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UK HMRC investigation windows 2025/26. Standard time limit: 4 years from the end of the tax year for "honest mistakes" or non-fraudulent under-declarations. Example: 2024/25 return (filed January 2026) can be re-assessed until 5 April 2029. Careless inaccuracy: 6 years window — if HMRC can show you should have been more careful. Deliberate inaccuracy: 20 years — for fraud, evasion, or deliberately under-reporting. Offshore matters: also 20 years since the Finance Act 2019 changes. Discovery assessments: HMRC can issue an assessment outside the normal window if they "discover" new information not available previously. Record-keeping requirements: at least 5 years past 31 January submission deadline for self-employed; 22 months past tax year end for employees. Limited companies: 6 years past the accounting period end. Triggered investigations: random selection (small %), red flags (large changes year-on-year, inconsistent third-party data from banks/employers, missing income visible to HMRC, complex offshore arrangements, lifestyle inconsistent with declared income). Penalties: 0-30% (careless), 20-70% (deliberate), 30-100% (deliberate concealed); reduced by up to 100% for unprompted full disclosure. Practical advice: if you realise an error, voluntarily disclose via the Digital Disclosure Service — much lower penalties than waiting for HMRC to find you.
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This answer is informational only and does not constitute financial, tax or legal advice. Figures are for the 2025/26 UK tax year. See our methodology and sources.