Inventory valuation requires lower of cost or net realisable value; cost encompasses purchase, conversion and attributable overheads. Inventories are measured at the lower of cost or net realisable value. Cost comprises costs of purchase (net of discounts, including duties and freight), costs of services (direct labour and attributable overheads), costs of conversion (direct costs and systematic allocation of fixed and variable production overheads based on normal capacity), and other costs necessary to bring inventories to their present location and condition. Exclusions include abnormal wastage, non-production storage, unrelated administrative overheads and selling costs. Cost formulas permitted are specific identification, FIFO, or weighted average; write-downs to net realisable value are required on an item or appropriate aggregate basis.