def formula_2009_01_01(foyer_fiscal, period, parameters):
    """
        Assiette régime microsocial pour les professions libérales
        """
    ebnc_impo_i = foyer_fiscal.members('ebnc_impo', period)
    P = parameters(period).impot_revenu.rpns.micro
    return foyer_fiscal.sum(ebnc_impo_i)
