def formula_2006(foyer_fiscal, period, parameters):
    """
        Somme totale des impôts moins restitutions et degrèvements
        """
    bouclier_imp_gen = foyer_fiscal('bouclier_imp_gen', period)
    restitutions = foyer_fiscal('restitutions', period)
    return -bouclier_imp_gen + restitutions
