Case C-578/21 P: Judgment of the Court (Seventh Chamber) of 17 November 2022 — Irish Wind Farmers’ Association Clg, Carrons Windfarm Ltd, Foyle Windfarm Ltd, Greenoge Windfarm Ltd v European Commission (Appeal — State aid — Article 107(1) TFEU — Article 108(2) and (3) TFEU — Regulation (EU) 2015/1589 — Article 4 — Member State legislation on business property taxation — Methods for valuation of property used to calculate the basis of assessment of the rate payable — Complaint from wind farm operators — Allegation of an under-assessment of the basis of assessment for the business rate payable by fossil fuel electricity producers and, consequently, of a level of business rate of those electricity generators lower than that of other electricity producers due to the choice of valuation method used — Preliminary examination procedure — Decision finding that there is no State aid — No economic and selective advantage — Failure to initiate the formal investigation procedure — Concept of ‘serious difficulties’ — Extent of the European Commission’s investigative duty — Principle of sound administration — Obligation to conduct the investigation procedure diligently and impartially — Scope of review by the General Court of the European Union)