Why an extra washbasin costs you tax in France

France once taxed doors and windows; that tax was only abolished in 1926. The idea hasn't entirely disappeared: a home's fittings still feed into property tax today. An extra washbasin in the guest WC really can increase your taxe foncière – and, for second homes, the taxe d'habitation.

How the tax office calculates

Both taxes are based on the valeur locative cadastrale, a notional annual rental value. It is derived from the so-called weighted floor area (surface pondérée):

• The starting point is the actual living area
• For each comfort feature, a flat area is added (équivalences superficielles)
• Adjustments are made for condition, location and build quality
• The result is multiplied by the municipality's rental value per m² and updated annually

What counts as comfort

Tax law sets fixed area equivalents, for example:

• Bathtub: 5 m²
• Shower: 4 m²
• Washbasin: 3 m²
• WC: 3 m²
• Sink: 3 m²
• Mains drainage connection: 3 m²
• Rubbish chute: 3 m²
• Lift: 4 m²
• Central heating: 2 m² per room
• Running water, electricity and gas: 4, 2 and 2 m²

So for the tax office, an extra washbasin makes your home 3 m² larger. The additional tax is usually modest – often a few euros to a few dozen euros a year – but it is payable every year. Some developers therefore deliberately leave the washbasin out of the guest WC.

Pools, extensions, garages: declaration is compulsory

Major changes must be reported to the tax office within 90 days of completion, now online under “Gérer mes biens immobiliers” on impots.gouv.fr. This includes:

• New builds, extensions and conversions adding living space
• Swimming pools
• Garages, carports and outbuildings
• Changes of use, e.g. garage into living space

The tax office now detects undeclared pools and extensions from aerial imagery, followed by back-taxation. New buildings can be exempt from taxe foncière for two years – but only if declared on time.

What this means for buyers

• Ask to see the last avis de taxe foncière before buying
• For houses with a pool or extension, check that they have been declared – otherwise a back-tax claim may follow after purchase
• Planning alterations? Factor the higher property tax into your running costs

How the two local taxes work and when they are due: Taxe foncière and taxe d'habitation.

All information without guarantee, as of November 2026. It is for general guidance only and does not replace legal or tax advice.