Indian Evidence Act, 1872
99. Who may give evidence of agreement varying terms of
document
Persons who are not
parties to a document, or their representatives in interest, may give evidence
of any facts tending to show a contemporaneous agreement varying the terms of
the document.
Illustration
A and B make a
contract in writing that B shall sell A certain cotton, to be paid for on
delivery. At the same time they make an oral agreement that three months’
credit shall be given to A. This could not be shown as between A and B, but it
might be shown by C, if it affected his interests.