20. NON-AVAILABILITY OF AN ADDRESS FOR SERVICE. - The Registrar may, at any time when a doubt arises as to the continued availability of an address for service in India entered in the register, request the person for whom it is entered, by letter directed to any other address entered in the register or if no such address is entered in the register to the address at which the Registrar considers that the letter would reach him, to confirm the address for service in India and if within three months of making such a request the Registrar receives no such confirmation, he may strike the entry in the register of the address for service in India and require such person to furnish a fresh address for service in India, or his address at the principal place of business in India, if he has any at that time. | 