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SubscribeThe Third Chamber of the Spanish Supreme Court ("SC") issued an order on November 11, 2025, in cassation appeal No. 5827/2023 (ECLI:ES:TS:2025:10520A), suspending proceedings and referring several questions to the Court of Justice of the European Union (CJEU) for a preliminary ruling on the compatibility of the Catalan tax on the emission of nitrogen oxide ("NOx") into the atmosphere produced by commercial aviation ("IEONA") with European Union (EU) law. It particularly questions compatibility with (i) article 14.1.b) of Council Directive 2003/96/EC of October 27, 2003, restructuring the Community framework for the taxation of energy products and electricity ("Directive 2003/96/EC"); and (ii) article 1.2 of Council Directive 2008/118/EC of December 16, 2008, on the general arrangements for excise duty and repealing Directive 92/12/EEC ("Directive 2008/118/EC").
What is the SC questioning?
The SC highlights the similarities between the IEONA and the Swedish tax examined in the Braathens judgment (C-346/97, EU:C:1999:291), which found the Swedish tax to be incompatible with the EU's mandatory exemption for aviation fuel from excise duties. The SC emphasizes that the Catalan tax has characteristics of an indirect tax because it effectively taxes the consumption of fossil fuels used in air navigation. Specifically, the preliminary referral requests an interpretation of whether: (i) article 14.1.b) of Directive 2003/96/EC opposes a tax like the IEONA that taxes the emission of NOx by commercial aircraft in airfields during the landing and take-off (LTO) phases; and (ii) article 1.2 of Directive 2008/118/EC—repealed by Directive 2020/262 of December 19, 2019, concerning general arrangements for excise duty, and which contains a provision analogous to the original—opposes an indirect tax "with no specific purpose" such as that established by Act 12/2014.
Key points from its reasoning: nature of the IEONA and its specific purpose
In the SC’s opinion, although the autonomous regional law invokes a non-fiscal environmental purpose, the IEONA’s legal framework does not show any mechanisms of impact that guarantee a direct link between the revenue collected and the environmental purpose—according to the doctrine of the Transportes Jordi Besora case (C-82/12, EU:C:2014:108)—nor does it show a dissuasive design that is consistent with that purpose. The order stresses that the taxable base is determined by the amount, in kilograms, of NOx emitted during the LTO phases using European Monitoring and Evaluation Program/European Environment Agency factors, and that the limit of 20,000 flights per tax period—which is no longer in force—is not in line with environmental logic, raising additional doubts on the design’s consistency.
Practical impact for operators and taxpayers
For airlines and operators active in Catalonia, the order anticipates scrutiny of the IEONA under the perspective of the directives on energy products and excise duties, with the possibility of the CJEU declaring it incompatible if it considers the tax to be an indirect tax without the required specific purpose, or that it interferes with the requirement exempting aviation fuel from excise duties.
It is worth examining the procedures currently underway, as well as the possibility of requesting new procedures for reviewing tax statements of non-statute-barred years, to safeguard the position of operators in the event of a positive ruling.
What happens now?
The CJEU must rule on the two questions raised by the SC, which focus on the mandatory exemption for aviation fuel and the compatibility of additional indirect taxes without a specific purpose with the general arrangements for excise duty. Its response will determine how the IEONA fits into EU law and will guide the dispute’s resolution before the SC.
For more information, please contact our specialists through the Knowledge and Innovation Area.
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