chapter  5
46 Pages

Power to Vary

Obligations under a contract cannot be varied unilaterally unless the contract provides for this. If a seller has agreed to supply a particular product, the buyer can normally only change that product by agreement. If the contract is to be varied, then the same requirements regarding mutual agreement and consideration apply, as they would in relation to entering into a new contract.1 Varying the scope of works under a construction contract involves changing the obligations of the contractor and this is no dierent, in principle, from varying any provision of the contract.2 An employer therefore has no implied unilateral right to vary the works.3