Under Section 35 of the Indian Stamp Act, 1899, an instrument chargeable with duty which is not duly stamped:

Section 35 of the Indian Stamp Act, 1899, provides that an instrument chargeable with duty shall not be admitted in evidence for any purpose, nor be acted upon, registered or authenticated, by any person having by law or consent of parties authority to receive evidence, unless it is duly stamped. The consequence is one of inadmissibility rather than voidness: a proviso to the section permits the instrument to be admitted in evidence on payment of the duty with which it is chargeable together with the prescribed penalty. Once an instrument has been admitted in evidence, Section 36 bars any later objection that it was not duly stamped. The instrument remains valid between the parties but stays out of court until the duty and penalty are paid.