In this article, we examine how a treaty can vary and the factors that courts will consider when considering whether a valid change has taken place. Sometimes it is not only wise, but essential to vary a contract in writing. Commercial contracts often contain a clause stating that an amendment is only effective if it is in writing and signed by all parties. This type of clause aims to strike a balance between flexibility and security. While allowing the parties to vary their agreement (giving the parties the opportunity to reflect subsequent developments and changes in practice), this means that the parties should always have a definitive record of the agreed terms (as they vary over time) and can therefore avoid disputes over the terms governing their relationship. However, there may be other reasons why the implementation of a supplementary agreement by instrument is a good step in such circumstances. One of them could be due to the fact that the underlying contract is itself an act and that there is an argument that an act can only be modified by a single act and not by a simple contract. The second reason why a document might be more appropriate is that the parties negotiate and compromise rights and claims arising from more than one contract. In these circumstances, a formal document should be more useful in the long run. However, until recently, there was some uncertainty as to the obligation of such clauses. Despite the clear wording of these amending clauses, they could have led to contradictory decisions by the English courts. In one case, the Court of Appeal decided that the parties could vary orally or behaviourally, even though the agreement explicitly states that the amendments must be made in writing. Essentially, the Court held that, when they orally agreed to vary a substantial part of their agreement, they also implicitly agreed that the “written amendment” clause no longer applied.
However, following a Supreme Court decision in May 2018, this approach is no longer a good right. Now, the parties may have more confidence that if their contract states that it can only be amended in writing, it is likely that the courts will ups down this provision. However, there may be limited exceptions where one party relies on the other`s assurance that an oral amendment is valid, regardless of the existence of such a clause. In such cases, the doctrine of legal effect may prevent the party from applying the “amendment in writing” clause. In this case, the party who claims that the contract has been amended must demonstrate that there is clear conduct that is inconsistent with the terms of the original contract and that corresponds only to the parties who have agreed to amend those terms. In other words, a party will not be able to establish a variation in conduct if the parties had acted or could have acted exactly as they did without such an agreed variation. . . .