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Municipalities Use Drones and Aerial Images to Review Property Tax. Properties with Undeclared Areas Already Generate Fines and Retroactive Charges in Several Cities.
In recent months, several Brazilian municipalities have adopted a new type of property inspection that promises to change the way property tax is collected. Cities such as Bauru (SP), Salvador (BA), Curitiba (PR), Goiânia (GO), and Belo Horizonte (MG) have begun to use drones, aerial images, and digital georeferencing systems to compare the official property listings with the physical reality. The result has been surprising: thousands of properties with undeclared areas have been identified, and their owners have started to receive notifications and retroactive property tax charges.
Technology Exposes Properties with Areas Different from the Declared
The initiative, which has been in effect since 2023, gained traction in 2025 with the modernization of municipal revenue systems.
According to data released by the National Confederation of Municipalities (CNM), more than 600 municipalities have signed contracts with specialized companies in aerophotogrammetry, a technology that uses drones to accurately measure land and buildings.
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These high-resolution images are cross-referenced with the tax registration of each property. When the system detects discrepancies between the actual built area and what was declared for property tax, the owner is notified to correct the registration and pay the retroactive difference. In many cases, the charge includes fines and interest for the past five years.
In Bauru (SP), for instance, the aerial recertification revealed over 7,000 properties with areas larger than those registered.
The municipality estimates an increase of R$ 12 million per year in revenue. In Salvador (BA), the city identified about 10,000 irregular constructions after using drones and began notifications for updating tax data.
Cross-Referencing Data with Registries and Utility Companies
In addition to aerial images, municipalities began to integrate their systems with public and private databases, such as information from property registry offices and even from energy and sanitation companies, aiming to detect indications of irregular occupations or undeclared alterations.
Although there is still no national rule for cross-referencing electricity accounts with property tax, many municipalities have been establishing technical cooperation agreements to share information that may indicate properties built without formal registration — especially in expanding urban areas.
This integration allows administrations to identify properties that do not pay property tax, expanded areas without permits, and new constructions that are still not regularized in the municipal tax registration.
Notifications and Retroactive Charges
When the irregularity is confirmed, the owner is officially notified to update the registration and settle the amounts owed.
If they do not comply within the deadline, the municipality can issue the retroactive debt, including interest, fines, and monetary correction, in accordance with Article 173 of the National Tax Code (Law No. 5,172/1966).
Some administrations, such as those of Curitiba and Goiânia, have used online portals that allow taxpayers to view the aerial map of the property and present defense or proof that the measurements are correct.
According to tax law specialists, these measures are legal and are supported by the principle of self-defense of Public Administration, which allows the municipality to review registrations and correct underreported amounts.
Direct Impact on Property Owners
In practice, the inspections have affected both small residential properties and large commercial buildings.
Owners who renovated, expanded, or built without notifying the municipality may now be surprised by property tax rates up to 40% higher and retroactive charges of up to five years.
In medium-sized cities, the impact is twofold: in addition to the increase in revenue, there is a valuation of the municipal database, which more accurately reflects urban development. However, tax lawyers warn of the need for prior notification and the taxpayer’s right to defense, under penalty of nullification of the charge.
National Trend and Advancement of Fiscal Digitalization
According to the CNM, the trend is for the use of drones and aerial images for fiscal purposes to become standard among Brazilian municipalities by 2027.
With advances in technology and federal government incentives for modernizing municipal tax collection, more cities are expected to adopt automated data cross-referencing systems and artificial intelligence to identify fraud and omissions in property registration.
For specialists, this movement marks the beginning of a new era of “smart property tax”, where municipalities operate based on data and digital evidence, reducing tax evasion and balancing the urban tax system.
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