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Privacy & law21 August 2026 · 2 min read

Section 171: re-identifying data is a crime in the UK

Few people know it, but in the UK it's a criminal offence to knowingly or recklessly re-identify de-identified personal data without the controller's consent.

What the law says

  • Section 171(1): re-identifying de-identified personal data without consent is an offence.
  • Section 171(5): so is knowingly processing data that has been re-identified.
  • Section 172: allows testing whether de-identification works, under conditions.
✓Data de-identified by the seller✓Buyer barred from re-identifying✓Re-identification is also a crime✓Effectiveness testing allowed (s.172)✓Breach triggers deletion duties✓Audit rights for the seller
How s.171 fits into a licence

Why it matters for sellers

It adds a legal backstop to the contract. Our licences restate the bar on re-identification and require deletion on request.

Key takeaways
  • Re-identification without consent is an offence.
  • Contracts should say so explicitly.
  • It's a backstop, not a substitute for proper de-identification.

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