Inventory valuation requires lower of cost or net realisable value with prescribed cost components and disclosure. Inventories for income computation must be measured at the lower of cost and net realisable value. Cost includes costs of purchase (purchase price, duties, freight less discounts), costs of services (direct labour and attributable overheads), costs of conversion (direct production costs and systematic allocation of fixed and variable overheads based on normal capacity) and other costs necessary to bring inventories to present location and condition. Abnormal wastage, non-production storage, unrelated administrative overheads and selling costs are excluded. Cost assignment uses specific identification for non-interchangeable items, and FIFO or weighted average for interchangeable items; write-downs to net realisable value are done item-wise or by product line where appropriate.