To make this change, use Form 3115. For a manufacturer, market applies to the basic elements of cost - raw materials, labor, and burden. If section 263A applies to the taxpayer, the basic elements of cost must reflect the current bid price of all direct costs and all indirect costs properly allocable to goods on hand at the inventory date. Also check the LIFO box on line 9c. On line 9d, enter the amount or the percent of total closing inventories covered under section 472.
Estimates are acceptable.
538 for more information on inventory valuation methods.