Who may give evidence of agreement varying term of document

People who are not parties to a document, or their representatives in interest, may give evidence of facts showing there was a contemporaneous agreement that varied the document's terms. It applies when an oral or side agreement made at the same time alters or contradicts the written document. The consequence is that such evidence can be used to prove the variation.

Priya signs a shop lease saying the tenant will pay all electricity. At the same time the landlord orally agrees with Arjun, who is not a party to the lease, that they will share the meter and split the bill. Arjun may give evidence of that contemporaneous agreement to show the written lease term was varied.