The First-tier Tribunal (General Regulatory Chamber) (FTT) has dismissed an appeal by a Manchester man seeking access to anonymised corporation tax data, ruling that even heavily altered records could still allow companies to be identified, and therefore must remain confidential.
In Nigel Demming v Information Commissioner & Anor (UKFTT 75 (GRC) [2026]), the FTT upheld a decision by the Information Commissioner and HM Revenue & Customs (HMRC) to refuse a Freedom of Information Act (FOIA) requesting anonymised corporation tax return data (CT600 forms) for millions of UK organisations.
The appellent, recruitment company CEO Nigel Demming, argued that the data could be safely anonymised using techniques such as removing identifiers and applying “K‑anonymity” banding, claiming this would eliminate any realistic risk of re-identification. He said the public had a legitimate interest in access to such microdata.
HMRC disagreed, insisting that even anonymised or pseudonymised records could allow companies to recognise their own filings or be identified through “mosaic” or “jigsaw” analysis using publicly available information, including Companies House records. The Information Commissioner accepted this view in 2025, prompting Demming’s appeal.
The tribunal panel - Judge Harris, Member Murphy and Member Scott concluded that taxpayer confidentiality laws override the Freedom of Information Act (FOIA). Taxpayer data is held for HMRC’s tax-collection functions and is protected under the Commissioners for Revenue and Customs Act 2005 (CRCA).
In respect of anonymisation, the tribunal found that even if only a company itself could recognise its own anonymised return, that is enough to trigger the statutory bar on disclosure.
The tribunal also accepted HMRC’s evidence that cross‑referencing anonymised data with public sources could reveal identities, especially for niche sectors or unusual tax relief combinations.
It also ruled that the FOIA does not require HMRC to create new datasets in order to comply with requests. Demming’s proposed transformations went beyond what FOIA obliges a public authority to do.
The tribunal found that Demming’s anonymisation model - though detailed - could not eliminate the possibility of identification or deduction of identity. Even rare combinations of financial fields, regional data, or tax reliefs could single out a company.
It also accepted HMRC’s argument that releasing individual-level tax microdata would never meet the standards of Statistical Disclosure Control used for official statistics, which are published only in aggregated form.
The tribunal dismissed the appeal in full, confirming that HMRC was entitled to rely on the absolute exemption under FOIA section 44(1)(a), which prohibits disclosure where another law- in this case, the CRCA - bars release.
