Under Registration Act 1908; on Re-Registration, the Registration shall be effective: 

As per Registration act, 1908   S. 23A. Re-registration of certain documents   Notwithstanding anything to the contrary contained in this Act, if in any case a document requiring registration has been accepted for registration by a Registrar or Sub-Registrar from a person not duly empowered to present the same, and has been registered, any person claiming under such document may, within four months from his first becoming aware that the registration of such document is invalid, present such document or cause the same to be presented, in accordance with the provisions of Part VI for re-registration in the office of the Registrar of the district in which the document was originally registered; and upon the Registrar being satisfied that the document was so accepted for registration from a person not duly empowered to present the same, he shall proceed to the re-registration of the document as if it has not been previously registered, and as if such presentation for re-registration was a presentation for registration made within the time allowed therefor under Part IV, and all the provisions of this Act, as to registration of documents, shall apply to such re-registration; and such document, if duly re-registered in accordance with the provisions of this section, shall be deemed to have been duly registered for all purposes from the date of its original registration: