Normally, for the purpose of accounting, fixed investment refers to "physical assets held for one year or more". The investment capital is therefore "fixed", in the precise sense that the capital is tied up in physical assets for a longer time, and thus cannot be used for other purposes. This contrasts with, for example, investment capital in the form of liquid bank deposits earning interest, or investment in raw materials completely used up in (say) five weeks to produce products which, upon sale, earn income the following month.
