This procedure must consistently identify and distinguish between costs and revenues, and between materials or services used up, fixed assets and new outputs, according to a standard valuation. In national accounts, this is especially important because the inputs of one enterprise are the outputs of another, and vice versa; lacking a consistent procedure, double counting would result. In turn, the "grossing and netting" procedure assumes a value theory and a definition of the coverage of production. Once we have that, we can aggregate a multitude of prices to obtain a price for the total value of net output.