AMP Limited's stock plummeted 5.39% during intraday trading on Thursday.

The decline followed the company's announcement that it has changed its cost allocation methodology across its business units and corporate center, primarily impacting technology and property costs. While AMP stated these changes do not affect its total controllable cost base or total net profit after tax, they have led to a restatement of reported underlying net profit after tax for individual business units for fiscal 2024 and the first half of fiscal 2025.

The market's negative reaction suggests investor concern over the restatements and the potential implications for the transparency of individual business unit performance, despite the company maintaining its overall financial guidance.