3.72 Products used for intermediate consumption should be recorded and valued at the time they enter the process of production. They are to be valued at the purchasers' prices for similar goods or services at that time.
3.73 In practice, producer units do not usually record the actual use of goods in production directly. They record the purchases intended to be used as inputs and the changes in the amounts of such goods held in inventory. Intermediate consumption has therefore to be estimated by subtracting from the purchases the changes in inventories of inputs (see paragraphs 3.120. – 3.124. for the correct valuation of the latter).