French tax office now uses AI to spot undeclared garden sheds and verandas

Got a shed at the bottom of the garden that you never told the taxman about? France's tax authority may soon spot it from the sky.

The DGFiP (France's public finance directorate) is extending its AI tool to garden sheds of more than 10 m², as well as verandas and other outbuildings.

What happened?

The programme is called "Foncier innovant". It automatically analyses aerial images to flag gaps between what homeowners declared and what actually stands on their land.

The AI was developed with consulting firm Capgemini and Google. It compares satellite and aerial images with cadastral data (France's official property records).

If it finds an anomaly, a tax agent examines the case. If the missing declaration is confirmed, the owner gets a request to regularise their situation.

Did it work so far?

Yes, at least from the taxman's point of view. Since 2022 the tool has tracked down 140,000 undeclared swimming pools in four years.

Those pools became liable for the taxe d'aménagement (a one-off local tax on building works). That brought in about 40 million euros for local councils.

Why does it matter to you?

The taxe d'aménagement is due when you dig a pool, build an extension or convert a garage into living space. It is the little sister of the taxe foncière (annual property tax), but you pay it only once, when the work is done.

The amount varies a lot with the type of work and your commune's rate. Outbuildings under 5 m² are automatically exempt. Some up to 20 m² can be too, depending on the local authority.

To declare, log in to your secure account on the tax website, open the "Biens immobiliers" (property) tab and fill in the form for residential premises.

What's next?

Checks will focus on structures over 10 m², which can serve as an extra room. Declaring late is better than being caught: if the authority finds it first, you could face back payments plus a surcharge for failing to declare and for the delay.

The move was no surprise. Back in 2022, when the pool checks went nationwide after a trial in nine departments, the DGFiP said it would later look for "other forms of buildings".