Glossary
Variation clause
A variation clause says how the signed contract can be changed. In England and Wales, if the clause requires changes to be in writing and signed, an oral variation is not effective: Rock Advertising Ltd v MWB Business Exchange Centres Ltd [2018] UKSC 24. The usual commercial form is a no-oral-modification line.
Last updated 28 October 2026
The document that carries a small change is often an addendum or a change order. The variation clause is the rule that says those documents count, and that a chat message does not. Pair it with the entire agreement clause so earlier talk stays out and later talk has to follow the form. See /clauses/entire-agreement.
On Contracts.io a variation is an edit on the same shared contract, agreed and e-signed. We built the product so you do not email “v4_final” Word drafts back and forth. Lex keeps one version; both sides see the mark; the executed version is the one with the new words in it.
Can we change a contract by email?
Only if the variation clause allows it, or if there is no formalities clause and both sides actually agree the change. After Rock Advertising, a clause that says “in writing and signed” is effective: an oral or informal variation will not rewrite the paper. An email can be writing; whether it is a signature depends on the clause.
What did Rock Advertising decide?
The Supreme Court held that parties who agree that their contract may be varied only in writing signed by them are bound by that method. An alleged oral variation of a licence fee failed. The decision is why no-oral-modification clauses now mean what they say in England and Wales.
How is a variation different from an addendum?
Variation is the legal act of changing the deal. An addendum is the short document that records it. A new statement of work is a variation of the relationship if the master says SOWs form part of the agreement, or it is a new job under standing terms.
How should we record a change on Contracts.io?
Edit the live contract, agree the mark, and e-sign the updated wording. That is a signed variation in the form Rock Advertising requires. Do not park the change in a side thread and leave the signed PDF untouched. If the change is a new job, issue a new statement of work.
A worked example
A services agreement says no variation except in writing signed by both parties. The client messages “add a ninth page, same fee.” The studio refuses to start until a one-page addendum names the extra page, the extra £600, and the new date, and both sides e-sign it on the same link as the original. The Slack message is not the variation.
How it shows up in a contract
Sample wording · our own drafting
No variation of this agreement is effective unless it is in writing and signed by or on behalf of each party. For this clause, an electronic signature on a version of this agreement that records the change is a signature in writing.
In Plain English
A change only counts if it is written down and both sides sign it. Signing the updated contract on a screen counts. A chat message does not.
Common mistakes
- Doing the extra work on a verbal “yes” when the paper requires a signed variation.
- Leaving the variation clause silent on e-signature, then arguing about whether a typed name counts.
- Stacking six informal emails instead of one addendum that states the new fee and date.
- Letting a new statement of work rewrite liability without saying it varies a named clause of the master.
What the legislation says
Where a contract contains a clause that variation must be in writing and signed by or on behalf of the parties, an oral variation is not effective. The parties have bound themselves to a specified method of variation and the court gives effect to it.
Source: Rock Advertising Ltd v MWB Business Exchange Centres Ltd, [2018] UKSC 24Checked 28 October 2026Pending lawyer review
Sources
- Rock Advertising Ltd v MWB Business Exchange Centres Ltd, [2018] UKSC 24Checked 28 October 2026Pending lawyer review
Frequently asked questions
What is a variation clause?
The rule that says how the signed contract can be changed. The usual form is “in writing and signed by both parties”.
Can we vary a contract by email or Slack?
Not if the clause requires a signed writing. Rock Advertising [2018] UKSC 24 gives effect to no-oral-modification clauses. An agreed edit on one shared link, e-signed, is the clean path.
How is a variation different from an addendum?
Variation is the legal act. An addendum is the short document that records it. See /glossary/addendum.
Does a new statement of work count as a variation?
If the master says SOWs form part of the agreement, yes — and an order-of-precedence line should say which paper wins. See /glossary/statement-of-work.
Related
The legal wording governsLast reviewed 28 October 2026Pending lawyer review