French tax authorities have updated the monetary erosion coefficients used to calculate the tax base on transfers for consideration of undeveloped land that has become buildable, applicable to disposals occurring in 2026. 

France’s tax authority (RFPI) announced on 11 February 2026 an update to the monetary erosion coefficients relevant to taxes on the sale of undeveloped land that has become buildable.

Under Articles 1529 and 1605 nonies of the General Tax Code (CGI), the tax base is generally the capital gain, calculated as the difference between the transfer price defined in Article 150 VA of the CGI and the acquisition price stated in the deeds, adjusted in line with the latest consumer price index excluding tobacco published by the National Institute of Statistics and Economic Studies (INSEE).

To simplify this calculation, taxpayers may use standard monetary erosion coefficients for qualifying sales carried out since 2012. The latest publication updates these coefficients for disposals occurring in 2026.