The Official letter No. 3175/TCT-CS dated 05 September 2012 about guiding the application of the ratio of value added to revenue.
According to this official letter, the business individuals, households do not perform or inadequately perform the regulations on accounting regime, invoices and vouchers as prescribed by law (including the business individuals and households pay VAT under the direct method and use invoices upon sale of goods & services or present contracts with the clear revenue but not determine the expense: the business individuals & household pay tax under presumption method are subject to application of the ratio (%) of value added to revenue .