Section 120
Estoppel against denying original validity of instrument
Chapter 13: Special rules of evidence
No maker of a promissory note, and no drawer of a bill of exchange or cheque, and no acceptor of a bill of exchange for the honour of the drawer shall, in a suit thereon by a holder in due course, be permitted to deny the validity of the instrument as originally made or drawn.
The Negotiable Instruments Act, 1881 (Act No. 26 of 1881). From the updated text on India Code, with later amendments. Being checked against the official copy; amendment notes are not shown yet.