What is a Contract Variation? How to Manage Changes Effectively in Business Contracts

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Consideration is a legal concept that means each party must give something of value to the other for the change to be binding. It doesn’t always have to be more money. For example, if a client agrees to give a supplier an extra two weeks to deliver a project (a benefit to the supplier), the supplier might agree to provide an additional report at no extra cost (a benefit to the client). This mutual exchange of new promises or benefits constitutes valid consideration.

If you receive a proposed variation that you do not agree with, you should respond promptly and clearly in writing. Your response should acknowledge their proposal, state that you do not accept the proposed changes, and reaffirm your commitment to the existing terms of the contract. Maintaining a polite and professional tone is important, but your rejection should be unambiguous to avoid any claim that you implicitly agreed.

Generally, yes. Courts in many jurisdictions, including the UK Supreme Court, have strongly upheld NOM clauses, ruling that if a contract says changes must be in writing, then oral modifications are invalid. However, there can be a very narrow exception called “estoppel” where one party makes a clear and unambiguous promise to waive the NOM clause, and the other party relies on it to their detriment. Relying on this is legally complex and risky; the safest course is to always assume the NOM clause is enforceable and get everything in writing.

It can be, but it’s not ideal. A chain of emails where one party proposes a clear change and the other party explicitly agrees to it can form a legally binding variation, provided the other requirements (like consideration) are met. However, this method is messy and can lead to ambiguity. It’s far better to consolidate the agreed-upon changes into a single, formal variation document that both parties sign, creating a clear and undisputed record.

Yes, but only if both parties expressly agree to it in writing and the law in your jurisdiction allows it. Retroactive variations can be risky because they may alter obligations that have already been performed or invoiced. If you need a change to apply to past work, the variation document should clearly state the effective date and reference the specific deliverables or terms it affects.

There’s no legal limit to the number of variations, but from a business and operational standpoint, too many amendments can make the contract cumbersome and prone to errors. As a general guideline, if the majority of the original terms have been altered or the changes significantly reshape the relationship, it’s often more efficient and less risky to draft a new contract that consolidates all the agreed terms.