If the first party has accepted it consistently, it can be implied that the new payment date is the middle of the month and not the first day of the month. 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.