In principle, it includes the (separately itemised) increase in the value of output inventories held, with or without a valuation adjustment reflecting average prices during the accounting of the given period of time.
In addition, many profits arising from the use of natural resources, land, and financial assets (in the form of interest income) will not be included.
The net operating surplus (NOS) is thus the residual balancing item in the product account, obtained as follows: In simple equations,
The impact of this on net value added is offset to some extent by the fact that a tenant, or lessee, incurs no asset depreciation, whereas an owner would.
In UNSNA, this property income does not constitute part of value added in production, and is therefore excluded from operating surplus (except for what is called the services of the financial, insurance and real estate industry).
It is "analogous" to what is "left over" when a business deducts its costs from sales revenue in order to arrive at its profit total.
However, the analogy is somewhat deceptive, insofar as the operating surplus in national accounts, as a component of value added, is not truly equal to real generic pre-tax profit receipts.
Therefore, this is one reason why the operating surplus cited in national accounts is likely to be lower than real generic pre-tax profit income.
An additional problem is the practice of shifting the declaration of profit income to another country where taxes are lower, by means of various financial manipulations.
In the Marxian view, obtaining generic profit income from sales is precisely the prime motivator of capitalist business activity, and therefore to present this income as a "generic residual balancing item" in national accounts without making its components explicit does no justice to the real economic relations involved.