All changes should be made in writing and accepted by each party. Parties should follow all contract instructions and verify whether third party approval or approval is required. In a recent Supreme Court decision[1] when one party claimed that an agency agreement had been amended to reduce the agent`s commission from 60% to 40%, one of the reasons the Court refused to implement the alleged amendment, namely that the agent did not receive consideration for the reduction of the commissions. In this case, the party resulting from the modification of the contract must demonstrate that there is a clear pattern of conduct that is inconsistent with the terms of the original contract and that is consistent only with the parties` agreement to change those conditions. In other words, a party will not be able to justify a change in behaviour if the parties had acted or acted exactly as they would have done in the absence of such an agreed amendment. It is therefore often very difficult to find that a contract has been altered by the behaviour, so it is wise for the parties to record the changes in writing in order to avoid disputes over the terms of their relationship. Changes to a construction contract are usually made by written agreement between the parties and are changes to the contractual provisions that do not include the scope of the work to be done. However, until recently, there was some uncertainty as to the binding nature of these clauses. Despite the clear wording of these variation clauses, they would have led to conflicting decisions of the English court. In one case, the Court of Appeal found that the parties could change their agreement orally orally or by conduct, even though the agreement expressly stipulates that the amendments must be made in writing. In essence, the Court held that, when they agreed orally to amend a substantial part of their agreement, the parties also tacitly agreed that the „written amendment“ clause no longer applied.

However, following a Supreme Court decision in May 2018, this approach is no longer a right. Now, the parties may have more confidence that the courts are likely to maintain this provision if their contract says it can only be amended in writing. However, there may be limited exceptions where one party relies on the other party`s assertion that an oral amendment is valid regardless of the existence of such a clause. In such cases, the Estoppel doctrine may prevent the party from „modifying s.a.“ – The application of the clause. This distinction may be important – if the amended agreement departs substantially from the original contract, it may be considered by the Tribunal as a new agreement, so that the original contract is cancelled.