Contracts as we known can exist in generally 2 forms. Which is either the contract is made in oral form or it is made in written form.
Both Oral and Written contracts are valid contracts which both are enforceable in court.
However, do you know that if the oral agreement is reduced into writing, any previous statement is not allowed to be admit as evidence. This is known as the parole evidence rule.
Which is in a way state that if previously there is an existence of an oral agreement or a statement is made before the written agreement, the oral agreement or statement may not be admitted as evidence and the Court will only consider the written terms of the contract. This is clearly stated in section 91 of the Evidence Act 1950.
However, there are several exceptions to the Parole Evidence Rule laid down in section 92 of the Evidence Act 1950. One of the methods to circumvent the Parole Evidence Rule is that to show that the oral agreement made exist together with the written agreement as a collateral agreement, however it is up to the Courts decision to decide whether the agreement does really exist collaterally.
Besides that, an oral agreement or statement may be admitted as evidence if it forms a condition precedent to the agreement. A condition precedent is defined as the oral agreement or statement itself is the sole purpose for the parties to enter into the written agreement.
Therefore, in order for the oral agreement or statement to be admitted as evidence, the relying party have to show either that the oral agreement or statement exist side by side with the contract or it forms a condition precedent to the contract.