Earnings in a period reflect the difference between revenue and cost of goods sold.

Iluka typically provides an outlook on cash and non-cash costs of production (operating depreciation and amortisation), as well as finished goods production volumes, which in periods of low and stable inventory levels will be a proxy for cost of goods sold.

In periods where inventory movements are significant, the below set of calculations can be used to estimate inventory movement from sales, unit cost of goods sold and D&A.

Method 1: Z/R/SR sales multiplied by Unit Cost of Goods Sold gives total Cost of Goods Sold
Method 2: The sum of D&A (operations excluding idle and corporate), Cash costs of production and Inventory movement gives total Cost of Goods Sold (equal to Method 1).

Use the Cost of goods sold calculated in Method 1 can be used to solve for inventory movement using the formula in Method 2 with other variables known or estimated.

The inventory movement calculated above includes cash and non-cash component. In recent periods, the cash component has accounted for 70-80% of inventory movement.

Cost of goods sold is the inventory value (cash and non-cash costs) of each tonne of finished product sold.  All production is added to inventory at cost with separate inventory stockpile values for each product (including heavy mineral concentrate (HMC) at mine sites) and location.  The inventory value used for each tonne of finished product sold is the weighted average value per tonne for the stockpile from which the product is sold.  

Inventories are valued at the lower of weighted average cost and estimated net realisable value. Weighted average cost includes direct costs and an appropriate portion of fixed and variable overhead expenditure, including depreciation and amortisation. Net realisable value is the amount estimated to be obtained from sale in the normal course of business, less any anticipated costs of completion and the estimated costs necessary to make the sale.

Inventories expected to be sold within twelve months after the balance sheet date are classified as current assets, all other inventories are classified as non-current assets.