Constitutional Court Ruling on Wind Farm Valuation Threatens 266 Council Lawsuits Over IMI on Dams and Turbines
A September ruling that the method used to value wind parks for IMI is unconstitutional now hangs over 266 council lawsuits against dam and wind operators, with 33.8 million euros at stake in the North alone.
A Constitutional Court ruling on how wind farms are valued for property tax now hangs over 266 lawsuits in which councils are trying to collect the Imposto Municipal sobre Imóveis (IMI, the municipal property tax) from companies that run dams and wind turbines, Público reported on 27 October. According to the newspaper, 135 municipalities host renewable energy production, and in the North alone 33.8 million euros of tax for the years 2008 to 2025 is in dispute.
What the court decided
The ruling is Acórdão n.º 777/2026, signed on 24 September by the four judges of the court's 3rd Section, which we reported in detail on 1 October. It concerned a property of the Portal da Freita wind park in the parish of Ansiães, Amarante, which the Tax Authority had valued at 285,440 euros. Público identifies the operator as Finerge.
The judges held that valuing wind parks by the "cost plus land value" method breaches the Constitution on two counts. Parliament never set the criteria for which properties are moved off the standard IMI formula, leaving that choice to a 2017 Finance Ministry order (Portaria n.º 11/2017), and Article 46(2) of the IMI Code names the method without defining its elements. The judgment covers wind parks only, but the order's list also sends dams to the same method, so the reasoning reaches the councils' claims on hydroelectric plants as well.
Why councils are worried
Público says the decision effectively spares the energy companies from paying anything to the councils in the pending cases. IMI is a municipal tax, so whatever is lost comes out of council budgets.
What it means for residents
- Your own IMI bill is not affected. Homes are valued under the standard formula in Article 38 of the IMI Code, whose factors the law spells out in full. If you think your home's value is too high, the separate revaluation route still applies (see our guide to DECO PROteste's advice).
- Council budgets in dam and wind areas may lose expected income, which Público says falls mostly on interior municipalities.
What happens next
The ruling binds only the Penafiel case it came from; no assessment is cancelled automatically. Under Article 281(3) of the Constitution, once the court has found a rule unconstitutional in three concrete cases, it may declare it unconstitutional with general binding force. Companies in the pending cases can rely on the same reasoning meanwhile.
The lasting fix lies with Parliament, which would have to write the valuation method into law. In January 2026 Finance Minister Joaquim Miranda Sarmento told MPs that a government working group on dam and power-plant valuation had finished, with the ANMP's agreement, and that the bill would reach Parliament "shortly", ECO reported. Wind projects in the interior remain contested on other grounds too, as the Serra do Marão decision showed last week.
