What happens if you provide goods or services for someone without a clear agreement on the precise terms of the arrangement? Most of the time you would be unable to collect if you cannot prove the existence of a contract, either written or oral. However, in some cases the law steps in to protect you under the doctrine of quantum meruit. Literally, the phrase means “as much as deserved”; the doctrine of quantum meruit is an equitable concept based upon the notion that one who benefits by the labor and materials of another should not be unjustly enriched thereby. Under such circumstances the law implies a promise to pay a reasonable amount for the labor and materials furnished even in the absence of a specific contract. The essential elements of the doctrine require a showing that valuable services or materials were furnished, that they were accepted by the person from whom recovery is sought and used and enjoyed by him, under circumstances where he should reasonably anticipate that the person performing the services or providing the materials expects to be paid for them.
— BBC&B