I.-The tax provided for in article 299 is based on the amount, excluding value added tax, as defined in IV of article 299 bis, of the sums received by the taxpayer, during the year in which the tax becomes due, in return for a taxable service provided in France.
However, sums paid in consideration for the provision of a digital interface that facilitates the sale of products subject to excise duty, within the meaning of Article 1 of Council Directive 2008/118/EC of 16 December 2008 on the general arrangements for excise duty and repealing Directive 92/12/EEC, are not taken into account where they have a direct and inseparable link with the volume or value of these sales.
II.-The amount of the tax is calculated by applying a rate of 3% to the base defined in I of this article.