Most NPIs are separately identified institutional units. That is, they are capable in their own right of owning assets, incurring liabilities and engaging in economic activities and in transactions with other entities. It follows that a complete set of accounts for the unit, including a balance sheet of assets and liabilities, exists or could be constructed if required. NPIs are categorized as follows: a. those providing services to corporations whose output is sold to the corporations concerned and treated as intermediate consumption; b. those that are controlled by government and provide individual or collective services on a non-market basis; c. those providing goods and services to households, divided between: those that provide goods and services to individual households at economically significant prices; those providing services to individual households free or at prices that are not economically significant and those that provide collective services free or at prices that are not economically significant.