On January 1, 2026, the provisions of the Mexico City Fiscal Code published in the Official Gazette on December 19 fully entered into force. Among the updated rates and fees, a collection mechanism that has been repeatedly challenged for its unconstitutionality persists: the artificial increase of the property tax base for “Special Installations.”
The 8% fiction
To determine the cadastral value of a property (the base on which the tax is paid), Mexico City’s rules require taxpayers to add a fixed percentage to the value of their construction if the building has special installations, accessory elements, or complementary works, such as elevators, air conditioning, fire-suppression systems, or other complementary works.
For 2026, the general rule imposes:
- An 8% increase for non-residential properties (offices, retail, and industrial).
- A 6% increase for residential properties.
The constitutional problem
This mechanism violates the principle of tax proportionality set forth in Article 31, Section IV of the Constitution.
Why? Because the law creates a “legal fiction.” The authority assumes, without contrary evidence, that special installations are automatically worth 8% of the construction value. This ignores economic reality: a new elevator in a smart building is not the same as an old system in an industrial warehouse. Because the real value (which is often much lower) is not taxed, the authority taxes wealth that does not exist.
The defense: an amparo proceeding
Federal courts have consistently granted amparos against this provision. The effect of a favorable judgment is to remove this fixed factor from the calculation. This allows the taxpayer to pay on the real value of the installations instead of a presumption of 8%, or to have the factor eliminated from the assessment, generating substantial recurring savings.
When to act
The indirect amparo must be filed within 15 business days following the first act of application. In most cases, that act is the PAYMENT of the property tax (whether the first two-month installment or the annual prepayment).
This communication is provided for informational purposes only and should not be considered professional advice.