ABSTRACT
Parties to a contract will normally wish to ensure that all their obligations are recorded in one agreement. They will also want to avoid evidential difficulties which may arise when one party to a contract alleges that the written agreement was amended or supplemented by oral representations and discussions. It is a common law principle that extraneous evidence cannot be used to vary a written contract. This rule is subject to a number of exceptions, in particular where the court is persuaded that the document does not reflect the entire agreement between the parties.
