French authorities have received an unexpected windfall in tax revenue after an artificial intelligence experiment discovered 20,356 undeclared swimming pools. Developed by Google and Capgemini, the software was launched as a trial last year to identify pools using aerial images and cross-check them with land-registry databases. Due to such a high volume of findings, officials have announced it will now be extended across the country in 2023.

Modifications to property must be declared to the tax office within 90 days of completion and as taxes are based on the rental value of the property, improvements result in an increase in taxes. According to French newspaper, Le Parisien, a typical pool of 30 square metres would be taxed an extra €200 a year, explaining why French authorities have accumulated a total of €10 million in revenue due to their recent findings.

There were reportedly 3.2 million private swimming pools in France before 2020, which has only increased since the pandemic due to high demand for outdoor improvements as more people were confined to their homes. The investigation arose as a result of environmentalists expressing concerns after summer heatwaves sparked drought and water restrictions nationwide. Once the investigation is rolled out across the country, the tax office has announced they’ll begin to look into the possibility of using the system to find undeclared annexes, extensions and verandas.