Man criticised by judge after using AI to fight £12,918 tax case

A taxpayer has been criticised by a judge after relying on an artificial intelligence chatbot to fight his tax case in court.

Marc Gunnarsson appealed against HM Revenue and Customs (HMRC), which sought to recover £12,918 in self-employment support payments he had claimed during the pandemic. Representing himself at the Upper Tribunal, Mr Gunnarsson used AI to draft his written submissions. However, the chatbot invented three tribunal cases that did not exist, which HMRC spotted in his skeleton argument filed the day before the hearing.

Judge Rupert Jones warned of the risks of relying on such tools. "The accuracy of AI should not be relied upon without checking, particularly when it comes to statements or arguments concerning the law. There is a danger that unarguable submissions or inaccurate, even fictitious, information or references may be generated," he said. The judge accepted that Mr Gunnarsson was not "highly culpable" because he had no legal training and may not have realised that the material produced was not just unreliable but fabricated. However, he cautioned that in other cases the tribunal "may take such matters very seriously."

Mr Gunnarsson had received two Self-Employment Income Support Scheme payments during the pandemic, believing in good faith that he qualified as self-employed. In fact, he was receiving income as a company director. The First Tier Tribunal initially sided with him, but HMRC appealed successfully. The Upper Tribunal ruled that the lower court had erred, allowing HMRC to recover the money.

The case reflects a wider trend of litigants turning to AI to prepare legal arguments, with courts increasingly forced to deal with the consequences when such technology goes wrong. AI systems are prone to generating information that appears credible but is false, a phenomenon known as "hallucination."

Similar problems have emerged in other recent cases. At the High Court, junior barrister Sarah Forey was accused of relying on AI after citing fictitious authorities in the defence of a homeless man. The judge described her conduct as "improper," "unreasonable," and "negligent," ordering her and her instructing solicitors to pay wasted costs. In another matter earlier this year, Bodrul Zzaman v The Commissioners for HMRC, a father appealing a £2,500 High Income Child Benefit Charge used AI to construct his submissions before the First Tier Tribunal. The arguments generated were irrelevant and his appeal was dismissed, with the judge observing that the case "highlights the dangers of reliance on AI tools without human checks to confirm assertions the tool is generating are accurate."

The Johnson Partnership, Nottingham