The oil industry uses as an underlying measure of performance replacement cost profit, rather than the more usual historical cost profit. Replacement cost profit excludes any losses or gains made on stocks of crude oil and products. The effect of this is to set against income the average cost of supplies in the accounting period rather than applying costs obtained by using the first in first out method. It therefore reflects more immediately changes in purchase costs. Replacement cost profit does not represent a formal accounting measure and is not reflected in the BP balance sheet.
Net debt equals finance debt less cash and current asset investments.