A more thorough explanation:

The substantial-performance doctrine is a rule that states that if a person makes a good-faith attempt to perform a contract but does not precisely meet the terms of the agreement or statutory requirements, the performance will still be considered complete if the essential purpose is accomplished. This is subject to a claim for damages for any shortfall.

For example, if a contractor builds a house but does not use the exact materials specified in the contract, but the house is still structurally sound and meets the essential purpose of providing a livable space, the contractor may still be considered to have substantially performed the contract.

Under the Uniform Probate Code, a will that is otherwise void because some formality has not been followed may still be valid under the substantial-performance doctrine. However, this rule is not widely followed.

The substantial-performance doctrine is different from the perfect-tender rule, which requires that goods delivered under a contract must precisely meet the terms of the agreement or the buyer can reject them.

Overall, the substantial-performance doctrine allows for some flexibility in contract performance while still holding parties accountable for any shortfalls.