The regions of Alpes-Maritimes, Var, Bouches-du-Rhône, Ardèche, Rhône, Haute-Savoie, Vendée, Maine-et-Loire and Morbihan were part of the trial - but tax officials say it may now be rolled out nationwide.

In France, permanently constructed pools increase property taxes because they boost a property's value. Pools are taxed by size and according to local tax rates; the average 30-square-meter pool, or roughly 323 square feet, costs the owner about 200 euros in taxes per year. Property taxes are paid to local municipalities. A small minority of France's 67 million citizens own swimming pools, but they have become increasingly popular in recent years. There are over 3 million private swimming pools in France, and over 240,000 were built in 2021 alone, according to France's Federation of Pool and Spa Professionals, an industry lobbying group.

The regions of Alpes-Maritimes, Var, Bouches-du-Rhône, Ardèche, Rhône, Haute -Savoie, Vendée, Maine-et-Loire and Morbihan were part of the trial - but tax officials say it may now be rolled out nationwide.

French tax authorities using AI software have found thousands of undeclared private swimming pools, landing the owners with bills totalling about €10m. The system, developed by Google and Capgemini, can identify pools on aerial images and cross-checks them with land registry databases. Launched as an experiment a year ago in nine French departments, it has uncovered 20,356 pools, the tax office said on Monday, and will be extended across the country. Modifications to property, including adding swimming pools, must be declared to the tax office within 90 days of completion. As property taxes are based on the rental value of the property, improvements mean an increase in taxes.