This guide is maintained as a current resource for September 2026 and covers only the laws of England and Wales. Information is for general guidance, not legal advice. Consult a qualified solicitor for advice specific to your situation.
Discover when verbal variations to contracts are legally valid in England and Wales. This detailed guide explains the enforceability of oral changes, the effect of “No Oral Modification” clauses, requirements for consideration, conduct as variation, and practical steps to ensure contract changes are binding.
Contracts can often evolve after they are first agreed. In commercial and business relationships, parties may seek to change terms by word of mouth rather than updating the written document. Whether such verbal variations are legally valid depends on a mix of statutory rules, common‑law principles, the wording of the contract itself, and practical evidence of agreement. This article explains when verbal variations are valid or unenforceable under the law of England and Wales, the key legal issues parties should consider, and how disputes over verbal changes are resolved.
Contract Variations: The Basics
A variation to a contract is simply a change to its terms after it has been formed. Under English law, contracts generally can be amended by agreement of the parties - and that agreement can be written, oral, or by conduct, unless the contract itself restricts how variations should be made. There is no general rule that variations must be in writing for validity, and oral agreements can be binding in principle if they meet the usual requirements for contracts (offer, acceptance, consideration or deed execution).
However, whether a verbal variation is legally effective depends on the contract's terms and the parties' intentions.
No Oral Modification (NOM) Clauses: Formality in Variations
Many commercial contracts include what is commonly called a “No Oral Modification” (NOM) clause. These provisions state that any variation must be in writing and signed by all parties before it takes effect. The UK Supreme Court has confirmed that such clauses are valid and enforceable in England and Wales, meaning that verbal changes will not be legally recognised if the contract expressly requires written variations.
Supreme Court Decision: Rock Advertising Ltd v MWB Business Exchange Centres Ltd
In Rock Advertising Ltd v MWB Business Exchange Centres Ltd [2018] UKSC 24, the Supreme Court upheld a NOM clause requiring variations to be in writing and signed. The court held that even though parties may agree orally to vary the contract, that oral agreement was ineffective because it did not comply with the contract's formal requirements.
The court emphasised that once a contract is formed, party autonomy applies only as far as the contract allows. If the parties have chosen formalities for variations, such as writing and signatures, the law will give effect to that choice. Verbal variations that do not comply with those formalities will not amend the contract.
Exceptions and Estoppel
There are limited exceptions. If both parties clearly agree to dis‑apply the NOM clause and do so in a way that indicates their intention (for example by written confirmation or conduct that unequivocally recognises the variation), a court may uphold the variation. Additionally, equitable doctrines such as estoppel may prevent a party from relying on a NOM clause to deny an oral variation if the other party has detrimentally relied on the informal change - though this is complex and fact‑specific.
Oral Variations and Consideration
Even where there is no NOM clause, a verbal variation may require fresh consideration (something of value exchanged) to be enforceable as a new contract. This stems from the common‑law rule that variations to a contract must either be supported by new consideration or executed as a deed to be binding. Without fresh consideration, an oral variation might be said to lack enforceability.
In some older cases, courts have emphasised this requirement, although the modern trend may allow a deed or other formal agreement to satisfy it.
Oral Variations by Conduct
In certain circumstances, a contract may be varied by conduct even without express written or verbal agreement. If both parties act consistently with the proposed variation (for example delivering goods on new terms and treating them as binding), a court may find that the contract has been varied by course of dealings. However, proof of this requires clear and consistent evidence of mutual conduct reflecting the variation.
Parties cannot easily rely on informal practice unless it is clear that both sides understood and accepted the new terms.
Proving Verbal Variations
Where a verbal variation is alleged, parties face evidential challenges. Unlike written changes, oral agreements often rely on testimony, emails confirming what was discussed, meeting notes, or conduct showing performance in line with the alleged variation. Courts will consider all relevant evidence in determining whether a verbal variation was intended and agreed.
Practical Considerations for Businesses
Check the Contract Terms
Before relying on a verbal change, check whether the contract contains a NOM clause or other formal variation procedure. If it does, the variation may be unenforceable unless the procedure is followed.
Confirm Changes in Writing
Even in the absence of a NOM clause, documenting variations in writing provides clarity, reduces disputes, and makes enforcing changes easier in courts or tribunals.
Agreement on Authority
Ensure that the person agreeing to the variation has authority to bind the business contractually. Even when a verbal variation might otherwise be valid, a party without proper authority may not bind the company.
Consideration or Deeds
Consider whether the variation needs fresh consideration or execution as a deed to be legally binding, particularly where the change affects rights or obligations materially.
Common Questions About Verbal Variations
Can a verbal variation override a written contract?
Yes, but only if there is no contractual restriction and the variation is supported by valid agreement and (where necessary) consideration. Where a NOM clause exists, it will generally prevent enforceability of purely verbal variations.
Are oral variations enforceable in business contracts?
Sometimes. In commercial contracts without formal variation requirements, verbal variations can be enforceable if there is clear agreement, evidence, and, if required, fresh consideration.
What if one party acts on a verbal variation?
Parties' conduct may amount to acceptance of a variation, especially where both sides clearly act in accordance with the new terms. However, this is often more difficult to prove than a written variation.
Key Takeaways
Verbal variations to contracts in England and Wales can be legally valid where there is mutual agreement and (if required) fresh consideration - and where the contract does not prescribe formalities for changes. However, where the contract includes a No Oral Modification clause requiring written and signed variations, the English courts will generally uphold those requirements and treat verbal changes as ineffective unless the clause is expressly abandoned or estoppel applies. Parties should therefore carefully review their contracts, confirm any agreed changes in writing, and gather clear evidence before acting on alleged verbal variations.
