What is a contract variation, and how do you check what it changed?
Law and last update: 2026-10-10
Short answer
A contract variation is an agreed change to the terms of an existing contract. Under English law it is binding if both parties agree, it is supported by consideration or made as a deed, and it follows any formalities the contract itself requires: the Supreme Court held in Rock Advertising v MWB (2018) that a clause requiring variations to be in writing and signed is effective. “Variation”, “amendment” and “addendum” are used largely interchangeably; what matters is what the document actually changes and from when.General information as of 2026-10-10, not legal advice.
What makes a variation binding
- agreement of the parties to the change;
- consideration for the change, or execution as a deed;
- compliance with the contract's own variation clause, e.g. a written variation signed by both parties (no oral modification clauses are enforceable);
- authority of the people who sign it.
Variation, amendment, addendum
In practice an amendment or variation replaces or deletes existing wording ("clause 5.2 shall be deleted and replaced by …"), while an addendum adds new terms. Construction contracts often use "variation" for a change to the works, which is different from a change to the contract terms. A deed of variation is a variation executed as a deed, common for leases.
How to check what a variation changed
Read each variation against the version it amends, not the original: later variations often amend clauses introduced by earlier ones. Check the operative wording (deleted, replaced, inserted), the clause references, and when the change takes effect, which may be a condition such as receipt of documents rather than a date.
KROTKA does this automatically: it puts the contract and all variations in one view and shows, for each change, the earlier and the new wording, changed amounts and dates, and the effective date, with verbatim quotes. It flags a variation that amends a clause which does not match its content, and gaps in the numbering.
Contract and variations in one view; up to 20 pages a month free.
Frequently asked questions
Does a contract variation need to be in writing?
Not as a general rule of English law, but if the contract requires variations to be in writing and signed, an oral variation is not effective (Rock Advertising Ltd v MWB Business Exchange Centres Ltd [2018] UKSC 24).
Is a variation the same as an amendment?
Largely, yes: both change an existing contract. An addendum usually adds new terms; a deed of variation is a variation executed as a deed.
When does a variation take effect?
When the variation says: on signing, on a stated date, or on a condition (for example an 'Effective Date' defined by receipt of documents).
Legal sources
This guide is for information only and is not legal advice. KROTKA does not provide legal advice.