Prélèvement à la source de l’impôt sur le revenu et année de transition. Quel impact pour les finances publiques et l’équité intergénérationnelle ?

The transition towards a withholding income tax system in 2019 in France introduces two tax changes. First, since taxes paid in 2018 and 2019 are based on income earned respectively in 2017 and 2019, income in 2018 will not be taxed, thus giving rise to a ?lost year? for public finances. In addition, taxpayers will lose the benefit of a one-year postponement in the tax payment, which constitutes an implicit tax increase. In this article, we evaluate the specific impacts of these two effects and the resulting global effect. The ?lost year? results in an annual income tax reduction that is proportional to the difference between the interest rate and the growth rate. Compensating the ?lost year? by an implicit tax increase induces the income tax receipt to increase proportionally to the nominal economic growth rate. From the taxpayers? viewpoint, we show that, whatever its precise modalities, the reform will weight unevenly in favor of the older generations to the detriment of the younger, and possibly the future, ones.