When parties want to change specific terms of an existing contract, they use an amendment or addendum. An amendment modifies existing clauses; an addendum adds new terms. Both require the same consideration and formalities as the original contract.

• Amendment: changes existing clauses
• Addendum: adds new clauses
• Both require mutual agreement and ideally consideration
• Should clearly identify the original contract and which clauses are changed
• Verbal variations: risky — always document changes in writing

Legal reference: Contract law (offer, acceptance, consideration); Contracts (Rights of Third Parties) Act 1999