Hoenig v Isaacs [1952] EWCA Civ 6 is an English contract law case concerning substantial performance of an entire obligation.

Somervell LJ upheld the decision of an Official Referee at first instance, His Honour Sir Lionel Leach, in finding there had been substantial compliance.

He noted the case was near the border line for substantial performance and disallowed the appeal.

He must pay it and bring a cross-claim for the defects and omissions, or alternatively set them up in diminution of the price.

The measure is the amount which the work is worth less by reason of the defects and omissions, and is usually calculated by the cost of making them good.