Why ChatGPT will silently lie about your bank statement (and how to catch it)

Every few weeks someone posts a victory-lap screenshot - "uploaded my bank statement to ChatGPT, got a clean spreadsheet back in 30 seconds." The spreadsheet looks pristine. Every date is formatted consistently, every merchant name is title-cased, every amount has two decimal places. The poster is happy. The replies are happy. The feature is "solved." It isn't. Those screenshots are the single most dangerous shape of LLM output for financial work, because the category of error in bank-statement