Inventory valuation at lower of cost and net realisable value mandates cost recognition, allocation rules and periodic write downs. Inventories are measured at the lower of cost and net realisable value. Cost includes costs of purchase, costs of conversion and other costs incurred to bring inventories to their present location and condition, while excluding abnormal wastage, certain storage and administrative costs, and selling costs. Costs of conversion incorporate direct labour and a systematic allocation of fixed and variable production overheads based on normal capacity. Items not ordinarily interchangeable use FIFO or weighted average; specific identification is required for segregated items. Net realisable value is assessed each balance sheet date and disclosures must state policies, cost formula and carrying amounts.