Taxe d’aménagement 2026: the French development tax on building works

Garden shed, conservatory, garage: the tax

Enclosed, roofed area

m²

Municipal + département rate

%

LocationOutside Île-de-FranceÎle-de-France

Development tax

€803

2026 value per m²	€892
Taxable value	€10,704
Exempt (5 m² or less)?	no

Full development tax calculator →

What counts as taxable space

The tax applies to works that need a permis de construire, a permis d’aménager or a déclaration préalable and that create taxable floor area: the inside surface of enclosed and roofed spaces with at least 1.80 m of headroom. Open terraces, pergolas and carports open on their sides create none; a closed conservatory, a garage or an attic converted into rooms do. A building of 5 m² or less is exempt outright, as is rebuilding identically within ten years of a demolition.

Some features are taxed by unit rather than floor area: a pool at €251 per square metre of basin, an outdoor parking space at €2,928 (up to €5,857 where the council decided so), ground-mounted solar panels, wind turbines over 12 m. Many foreign buyers discover the tax only when the bill arrives after the renovation of a country house; running the calculation before applying for permission avoids the surprise.

Why the town and the département set the price

The flat value per square metre is the same everywhere outside Île-de-France; the rates make the difference. Each département votes one rate for its whole territory, up to 2.5 %: 57 of 101 départements charge the maximum and the lowest charge 0.8 %. 17 départements changed their rate on 1 January 2026. Municipalities vote their own: of the 29,607 that set a single rate, 7,433 charge 5% and 21 go higher across their whole territory.

The calculator reads both rates from the deliberations the DGFiP publishes, taking for each authority the latest final decision in force on 1 January 2026. Where a town only votes rates by sector, or has not introduced the tax, the field is left for you to complete with the rate from the town hall.

The main-home allowance

The first 100 square metres of a main home and its annexes are taxed on half the flat value: €446 instead of €892 per m² outside Île-de-France. A holiday home, a gîte or a garden studio for guests gets no allowance, which is why the same project can cost almost twice as much for a second-home owner. Councils may also exempt, wholly or partly, homes financed with a zero-interest loan or garden sheds of 20 m² or less.

Lower values in 2026

The flat values follow Insee’s construction cost index, as last published on 1 January. For 2026 that is the third-quarter 2025 index, 2,056, against 2,143 a year earlier, so the value per square metre falls to €892 outside Île-de-France and €1,011 inside it. The rate that applies is the one in force when the permission is granted or the prior declaration is cleared.

Declaring and paying

Declare the works on impots.gouv.fr, under “Biens immobiliers”, within 90 days of completion, together with the property declaration that feeds the taxe foncière. The bill follows; above €1,500 it comes in two instalments. For a self-build, the tax adds to the price of the plot, the notary fees on the land and the works: the total cost calculator brings them together.