Which? Tests Find AI Chatbots Giving Wrong UK Money Advice, Including on ISA Allowance

Summary

Consumer group Which? tested six AI tools (ChatGPT, Google Gemini, Gemini AI Overviews, Microsoft Copilot, Meta AI and Perplexity) on 40 consumer questions across money, legal, health and travel topics. Asked how to invest a '£25k annual ISA allowance' (the real limit is £20,000), ChatGPT and Copilot missed the error and gave advice that could lead someone to oversubscribe to ISAs in breach of HMRC rules; Gemini, Meta AI and Perplexity corrected it. Which? also found tools pointing users to paid tax-refund firms alongside the free HMRC route.

Who caught it A researcherFound outside the organization

This is a study: context for the failures library rather than an incident at one organization, so it carries no lesson.

Key dates

1. November 18, 2025Event
2. October 16, 2026Checked against sources
3. October 21, 2026Checked against sources

Developments are added when the record is reviewed. Next review: October 16, 2027.

Evidence

Each passage is quoted from its source. The quoted passages are re-checked against the live pages every month.

1. Under controlled lab conditions, Which? tested six AI tools – ChatGPT, Google Gemini, Gemini AI Overview (AIO), Microsoft’s Copilot, Meta AI and Perplexity – to establish how well they could answer common consumer questions

   Supports: Tester, tools tested, date (November 18, 2025)

   ChatGPT and Gemini among AI tools giving risky consumer advice, Which? finds Which? Primary source

2. We placed a deliberate error in this question (the ISA allowance is 20k), and ChatGPT and Copilot missed it entirely.

   Supports: ISA allowance error

   Can you trust AI? ChatGPT and other AI chatbots put to the test Which? Primary source