What happens if only part of a contract is performed in Ontario?

When a party performs only part of what a contract required, the outcome depends on whether the contract is "entire" (requiring full performance as a condition of payment) or divisible (allowing payment for each completed part).

For entire contracts, a party who performs only part of what was required cannot generally claim the full contract price. However, the law of unjust enrichment and quantum meruit may allow recovery of the reasonable value of the work actually performed, to prevent the receiving party from getting a windfall.

Quantum meruit — "as much as has been earned" — is a restitutionary remedy that compensates for the value of partial performance even where no payment is formally due under the contract. Ontario courts will award it where the receiving party accepted and benefited from the partial performance and it would be unjust for them to pay nothing.

The innocent party may also have a counterclaim for the cost of having the remaining work completed elsewhere, or for the deficiency between what was delivered and what was promised. These claims run against each other.

If you are on either side of a partial-performance dispute, careful documentation of what was done, what was accepted, and what remains incomplete is essential to protecting your position.