The bill modifies the Internal Revenue Code concerning deductions for theft losses. It removes the limitation on deductions for personal casualty losses and specifies that such losses from theft involving fraud, deceit, or misrepresentation will be treated as sustained in the year of discovery. It extends the period for refund claims related to theft losses involving fraud. Furthermore, it amends the rules for distributions related to such losses, allowing repayments and modifying the period for credit or refund claims. Effective dates for the amendments are specified. Additionally, the bill addresses pyrrhotite-related personal casualty losses, defining them and extending the period for credit or refund claims relevant to such losses.