TL;DR: The PFU refers to the flat-rate taxation applied to income from movable capital, including dividends. It differs from taxation according to the progressive income tax scale, which applies when you exercise the option provided for in Article 200 A of the CGI.
Definition of the PFU on dividends
The PFU corresponds to the “flat-rate taxation” provided for in 1 of Article 200 A of the General Tax Code. It constitutes the flat-rate regime applicable to income from movable capital, which includes dividends.
PFU or progressive tax scale
You may be subject to flat-rate taxation or exercise the option provided for in Article 200 A of the CGI to subject your income from movable capital to the progressive income tax scale.
The progressive tax scale is therefore a mechanism distinct from flat-rate taxation.
The 40% allowance
The 40% allowance concerns distributed income included in the overall net income subject to the progressive tax scale, subject to the eligibility conditions provided for by the CGI.
This allowance is therefore linked to the option for the progressive tax scale and does not constitute a rule of flat-rate taxation.