Double counting (accounting)
Double counting in accounting is an error whereby a transaction is counted more than once, for whatever reason. But in social accounting it also refers to a conceptual problem in social accounting practice, when the attempt is made to estimate the new value added by Gross Output, or the value of total investments. What is the problem? In the case of a small individual business or having such utility, it is unlikely that an expenditure of funds, an input or output, or an income from production will be counted twice. If it happens, that's usually just  bad accounting (a math error), or else a case of fraud. But things are more complicated when we aggregate the accounts of many enterprises, households and government agencies ("institutional units" or transactors in social accounting language). Here, a conceptual problem arises. The basic reason is that the "income" of one institutional unit is the "expenditure" of another, and the "input" of one institutional unit is the "output" of another. If therefore we want to measure the total value-added by all institutional units, we need to devise a consistent procedure for "grossing and netting" the incomes and outlays of all  units, within a system of transactors. Lacking such a system, we would end up double counting incomes and expenditures of interacting units, exaggerating the quantity of value-added or investments. To estimate the annual net output of a country, for example, the cost of goods and services used up is deducted from gross revenue, all flows are valued uniformly, and flows which fall outside the production boundary are excluded. Value theory. The system of gross and netting actually used, is ultimately based on a value theory, which specifies what may generally count as: In other words, we cannot relate , group and aggregate prices in different ways without making some value-based assumptions that enable valid comparisons. Without those value assumptions, the aggregates themselves would be meaningless. Thus, when economists focus on market-prices, value assumptions are always in the back of their mind, even if they are not aware of that, and regard value theory as metaphysical. Counting units. Once the principles of the value theory are established, categories and counting units can be exactly and logically defined, as a basis for mathematical operations to aggregate the flows of incomes and expenditures. All flows can then be allocated to  their appropriate category, without counting the same flow several times. In fact, the value theory applied in national accounts is nowadays strongly influenced by the valuation principles of ordinary business accounts and the prevailing social relations governing economic exchange, often fixed by law. Thus, for example, it is argued that no new value can result from a "unilateral" transfer of funds, i.e. where funds are provided without anything being provided in return. The implicit assumption made in national accounts, is that the account at the macro-level must be similar to that at the micro-level. Economic relations are regarded  as broadly the same at the micro-level and the macro-level. An individual business buys and uses up inputs and produces outputs for sale; it has costs and revenues. Thus, in social accounting all transactors are treated in a similar way ("as if" they were a business). The accounts can be criticised for being eclectic in some ways, but that is not necessarily a problem; the aim of the exercise is to identify and categorise all flows, and the user can then reaggregate them in different ways. Persistent double counting problems. However, even if a consistent system of accounting  rules is devised that "conceptually" eliminates double counting, double counting may technically still occur to some extent.