R v Ron Engineering and Construction (Eastern) Ltd,[1] of 1981 is the leading Supreme Court of Canada decision on the law of tendering for contracts.

The case concerned the issue of whether the acceptance of a call for tenders for a construction job could constitute a binding contract.

The submitted tenders were opened by the owner and Ron Engineering was the low bidder by a substantial margin.

The Ontario Court of Appeal reversed the trial decision and held, relying on the contractual doctrine of mistake, that Ron Engineering was entitled to get its deposit back.

The tender, despite its being the product of a mistaken calculation, could be subject to the terms and conditions of contract A so as to invoke forfeiture of the deposit.

The issue did not concern the law of mistake but the application of the forfeiture provisions contained in the tender documents.