Persons subject to the obligations set out in article 242 ter, who pay income from transferable securities mentioned in 3 of article 158 to persons subject to the same obligations and to bodies or companies mentioned in 4° of 3 of the same article, identify at the time of payment the portion of this income eligible for the 40% allowance mentioned in 2° of 3 of the aforementioned article 158. Proof of this identification is kept available for the tax authorities.