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Harber v. HMRC
First-tier Tribunal (Tax Chamber) · Dec 4, 2023
GBEditorial impact: lowpro setrial
Direct answer
What happened in this matter?
Outcome: No Sanction on Litigant; Warning implied for lawyers.. AI UseCatherine Harber, a self-represented taxpayer appealing an HMRC penalty, submitted a document citing nine purported First-Tier Tribunal decisions supporting her position regarding "reasonable excuse". She stated the cases were provided by "a friend in a solicitor's office" and acknowledged they might have been generated by AI. ChatGPT was mentioned as a likely source.Hallucination DetailsThe nine cited FTT decisions (names, dates, summaries provided) were found to be non-existent after checks by the Tribunal and HMRC. While plausible, the fake summaries contained anomalies like American spellings and repeated phrases.…
- Why the court cared
- The Tribunal emphasized that submitting invented judgments was not harmless, citing the waste of public resources (time and money for the Tribunal and HMRC). It explicitly endorsed the concerns raised in the US Mata decision regarding the various harms flowing from fake opinions. While lenient towards the self-represented litigant, the ruling implicitly warned that lawyers would likely face stricter consequences. This was the first reported UK decision finding AI-generated fake cases cited by a litigant
- Why it matters now
- UK tribunals excused the pro-se taxpayer but telegraphed that solicitors filing the same fake cases will be punished.
Why this matter is tracked
Outcome: No Sanction on Litigant; Warning implied for lawyers..
AI Use
Catherine Harber, a self-represented taxpayer appealing an HMRC penalty, submitted a document citing nine purported First-Tier Tribunal decisions supporting her position regarding "reasonable excuse". She stated the cases were provided by "a friend in a solicitor's office" and acknowledged they might have been generated by AI. ChatGPT was mentioned as a likely source.
Hallucination Details
The nine cited FTT decisions (names, dates, summaries provided) were found to be non-existent after checks by the Tribunal and HMRC. While plausible, the fake summaries contained anomalies like American spellings and repeated phrases. Some cited cases resembled real ones, but those real cases actually went against the appellant.
Ruling/Sanction
The Tribunal factually determined the cited cases were AI-generated hallucinations. It accepted Mrs. Harber was unaware they were fake and did not know how to verify them. Her appeal failed on its merits, unrelated to the AI issue. No sanctions were imposed on the litigant.
Key Judicial Reasoning
The Tribunal emphasized that submitting invented judgments was not harmless, citing the waste of public resources (time and money for the Tribunal and HMRC). It explicitly endorsed the concerns raised in the US Mata decision regarding the various harms flowing from fake opinions. While lenient towards the self-represented litigant, the ruling implicitly warned that lawyers would likely face stricter consequences. This was the first reported UK decision finding AI-generated fake cases cited by a litigant
Operational lesson
UK tribunals excused the pro-se taxpayer but telegraphed that solicitors filing the same fake cases will be punished.
Record details
CourtFirst-tier Tribunal (Tax Chamber)
Jurisdictioninternational
CircuitNot recorded
DateDec 4, 2023
UN
AI toolUnidentified
Party typePro Se Litigant
OutcomeNo Sanction on Litigant; Warning implied for lawyers.
Known amountNot recorded
Professional sanctionNo
Attribution boundary
What the record establishes about AI use
not established
The current record does not establish a specific AI tool. Do not infer AI use beyond the source.
Procedural posture
No Sanction on Litigant; Warning implied for lawyers.
Correction behavior
Correction behavior is not separately verified in the current record.
Questions this record answers
- What happened in Harber v. HMRC?
- Outcome: No Sanction on Litigant; Warning implied for lawyers.. AI UseCatherine Harber, a self-represented taxpayer appealing an HMRC penalty, submitted a document citing nine purported First-Tier Tribunal decisions supporting her position regarding "reasonable excuse". She stated the cases were provided by "a friend in a solicitor's office" and acknowledged they might have been generated by AI. ChatGPT was mentioned as a likely source.Hallucination DetailsThe nine cited FTT decisions (names, dates, summaries provided) were found to be non-existent after checks by the Tribunal and HMRC. While plausible, the fake summaries contained anomalies like American spellings and repeated phrases.…
- Why does Harber v. HMRC matter for legal AI risk?
- UK tribunals excused the pro-se taxpayer but telegraphed that solicitors filing the same fake cases will be punished.
- What does the public record establish about Harber v. HMRC?
- The record summarizes the outcome described in the linked public source. The recorded link is a secondary or other public source and should be checked against the docket where available. This page is not a substitute for the complete docket, subsequent history, or jurisdiction-specific advice.
- Which source supports this Harber v. HMRC summary?
- The recorded source is bailii.org. It is classified as secondary or other linked source; review the linked material and subsequent docket history before relying on this summary.
Related matters
Related by court, jurisdiction, tool, or classified failure pattern. Similarity does not imply the same facts or outcome.