AMP (ASX:AMP) has changed its cost allocation methodology across its business units and corporate centre, primarily impacting technology and property costs, according to a Thursday filing with the Australian bourse.

The changes, mainly to better reflect its operating structure between the units and the group, follow a review on the heels of a cost-reduction program and do not impact the company's total net profit after tax (NPAT) or total controllable cost base.

However, the updates have led to a restatement of reported underlying NPAT for individual business units for fiscal 2024 and the first half of fiscal 2025.

For fiscal 2024, AU$48 million has been re-allocated from the group to the business units, and AU$25 million was re-allocated in the first half of 2025.

The company sees fiscal 2025 costs to be in line with guidance and projects fiscal 2026 controllable costs in the range of AU$630 million to AU$640 million.

Shares fell nearly 5% in recent Thursday trading.