HMRC v. Gunnarson
Upper Tribunal (Tax and Chancery Chamber) · Jul 23, 2025
What happened in this matter?
The respondent, an unrepresented litigant, included three fictitious case citations in his skeleton argument after using generative AI for research. The Upper Tribunal identified the error following HMRC's verification, and the respondent subsequently removed the fabricated authorities. The tribunal issued a warning regarding the responsibility of litigants to verify AI-generated submissions.
- Why the court cared
- The UT reasoned that while the respondent was not highly culpable as a lay litigant, the use of AI to generate fictitious citations is a serious matter. The tribunal highlighted that parties remain responsible for the accuracy of all submissions and that AI-generated content must be independently verified to prevent the introduction of misleading or fictitious information into court proceedings.
- Why it matters now
- Opposing counsel will independently verify skeleton citations; expect HMRC-level scrutiny in any tax appeal.
Why this matter is tracked
In an appeal concerning the recovery of coronavirus support payments, the unrepresented respondent submitted a skeleton argument containing three fictitious First-tier Tribunal (FTT) case citations. HMRC identified that these cases did not exist. Upon challenge, the respondent admitted to using generative AI to assist in drafting his submissions and subsequently filed an amended skeleton argument. The Upper Tribunal (UT) noted that while the respondent was not highly culpable due to his status as a lay litigant, the incident highlights the risks of AI-generated hallucinations in legal proceedings. The UT emphasized that all parties, including unrepresented litigants, are responsible for the accuracy of information presented to the tribunal and must independently verify AI-generated content.
Opposing counsel will independently verify skeleton citations; expect HMRC-level scrutiny in any tax appeal.
Record details
What the record establishes about AI use
The respondent admitted to using online AI software but did not specify the tool.
Appeal to the Upper Tribunal (Tax and Chancery Chamber) from a First-tier Tribunal decision regarding the recovery of SEISS payments.
Correction behavior is not separately verified in the current record.
Tracked discrepancy record
4 citation, quotation, or authority issues are recorded in the source dataset.
- Fabricated: Case Law | Respondent’s skeleton cited a non-existent FTT authority said to show HMRC’s SEISS guidance was unclear; UT records HMRC checked and the case does not exist.
- Fabricated: Case Law | Respondent’s skeleton cited a non-existent FTT decision claiming reliance on accountant’s advice and guidance was relevant; UT notes HMRC verified the case does not exist.
- Fabricated: Case Law | Respondent’s skeleton cited a non-existent FTT decision asserting a purposive approach allowed SEISS based on continuity of work; UT records the citation is fictitious.
- Misrepresented: Legal Norm | FTT applied an ‘honest belief’ eligibility test not found in the SEISS Directions or FA 2020; UT held this was a legal error.
Questions this record answers
- What happened in HMRC v. Gunnarson?
- The respondent, an unrepresented litigant, included three fictitious case citations in his skeleton argument after using generative AI for research. The Upper Tribunal identified the error following HMRC's verification, and the respondent subsequently removed the fabricated authorities. The tribunal issued a warning regarding the responsibility of litigants to verify AI-generated submissions.
- Why does HMRC v. Gunnarson matter for legal AI risk?
- Opposing counsel will independently verify skeleton citations; expect HMRC-level scrutiny in any tax appeal.
- What does the public record establish about HMRC v. Gunnarson?
- The record summarizes the outcome described in the linked public source. The recorded document is hosted in the upstream publisher archive. This page is not a substitute for the complete docket, subsequent history, or jurisdiction-specific advice.
- Which source supports this HMRC v. Gunnarson summary?
- The recorded source is Damien Charlotin case archive. It is classified as publisher document archive; 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.