The Supreme Administrative Court has overturned a judgment on fuel charges on CNG – the absence of a statutory conversion rate was key to the decision.
Experts from the Tax Practice have represented a company trading in natural gas (CNG) and holding the status of gas intermediary in a dispute over fuel charges. The National Revenue Administration authorities had imposed a fuel charge on the company on CNG intended for use in internal combustion engines, calculating the amount based on their own conversion of gas volume (m³) to mass (kg) using a physics formula based on its density.
The key issue in the dispute was the admissibility of the conversion. The Act on Toll Motorways and the National Road Fund sets the fuel charge rate exclusively in zloty per 1,000 kg, whereas natural gas is traded in units of volume – and the legislation does not provide for a conversion rate between these units. The tax authorities and the Voivodship Administrative Court in Gliwice concluded that the use of the physics formula was sufficient and did not contravene the law. On 14 January 2026, following a cassation appeal prepared by DZP's experts, the Supreme Administrative Court overturned the judgment of the Voivodship Administrative Court in Gliwice and referred the case back for re-examination.
In the cassation appeal, the DZP team argued that the only constitutionally permissible solution was for the legislator to introduce a clear volume-to-mass conversion rate directly in the legislation – without this element, the basis for calculating the public levy did not meet the requirements set out in Article 217 of the Polish Constitution. It was pointed out that shortcomings in the structure of a public levy cannot be remedied by non-statutory calculation methods, even if they are correct from a physics perspective, as this would lead to the tax authorities effectively creating law. This objection was consistently raised at every stage of the proceedings.
On 14 January 2026, the Supreme Administrative Court concurred with this argumentation and overturned the judgment of the Voivodship Administrative Court in Gliwice, referring the case back for re-examination. The Court agreed that any assessment of the legality of decisions made by the tax authorities must consider whether they comply with Article 217 of the Polish Constitution, and the fact that the court of first instance had failed to address this objection prevented a review on appeal and constituted a material defect in the judgment (case no. I GSK 472/23 and case no. I GSK 269/23).
The judgment is of significant importance not only for DZP’s client, but for all entities trading in CNG. It confirms that the components of a public levy – including the basis for its calculation – must derive directly from the legislation and cannot be reconstructed using non-statutory methods, even if these are correct from a scientific perspective.
This case demonstrates how crucial the correct structure of the tax base is from a constitutional perspective, a fact which the tax authorities, however, fail to take into account. The position that the structural elements of taxes cannot be derived from non-statutory sources has already been put forward in a case involving the taxation of acetylene, handled by the Tax Practice. These cases illustrate how important it is to raise arguments based on constitutional provisions when dealing with the tax authorities.
The case was handled by Tax Practice partners Jan Czerwiński and Artur Nowak, supported by Marta Wieczorek (Senior Tax Consultant).