धारा 91

When the maker or drawer of any bill of exchange, hundi or cheque has placed thereon any signature in token of his having accepted or drawn the same, or when any such bill, hundi or cheque has been altered by erasure, obliteration or otherwise, without the assent of the maker or drawer, the burden of proving that such signature was placed thereon or that such alteration was made with the assent of the maker or drawer, shall be on the person who asserts the validity of such signature or alteration. When the maker or drawer of any bill of exchange, hundi or cheque has placed thereon any signature in token of his having accepted or drawn the same, the burden of proving that such signature was placed thereon without his assent, shall be on the person who asserts the want of such assent.