The special tax on the sales of certain hydrocarbons is a tax of an indirect nature that falls on the consumption of those, taxing in a single phase, the retail sales of the products included in its objective scope, in accordance with the provisions of this Law (article 9 of Ley 24/2001). The hydrocarbons that are included in the objective scope of this Tax are gasoline, diesel, fuel oil and kerosene; liquid hydrocarbons used as heating fuel; and other equivalent gaseous products are intended to be used as propellant, as fuel additives or to increase the final volume of a fuel (with the exception of natural gas, methane, liquefied petroleum gas). The tax base shall consist of the volume expressed in thousands of litres, and metric tonnes in the case of fuel; and, it is determined under a direct estimation regime.

As a result of the integration of the special tax on the sales of certain hydrocarbons in the tax on hydrocarbons (Disposición adicional séptima of Ley 2/2012), in the Basque Country this tax is replaced by an autonomous rate of the tax on hydrocarbons (Disposición transitoria decimotercera of Ley 7/2014, 21 April).