In order to qualify for the input tax deduction (VAT return) an invoice must contain the taxpayer identification number or the VAT identification number, the quantity and type (commercial name) of the delivered goods and the scope and nature of all services performed at the time of delivery. The deciding factor on whether or not the input tax deduction qualifies is whether or not the billing information enables the tax authorities to control the payment of value added tax. Nevertheless, there can be no excessive or unreasonable requirements charged to the bill. For example, in an individual case if the circumstances indicate that a service was performed in a particular month in which the invoice was issued, it is not required for this sentence to be written in the invoice. The tax office cannot rely solely upon its own examination of the invoice and must consider supplementary information provided by the taxpayer.