What it means
Quantum meruit is Latin for 'as much as is deserved'. It allows a person to recover a reasonable amount for work done or services provided where there is no enforceable contract setting a price, or where work was done outside the contract at the other party's request. It is based on the principle that one party should not be unjustly enriched at another's expense. In Australia, courts assess what is fair and reasonable for the work, which is not necessarily the same as the profit the claimant hoped to make.
How it's used
When the contract turned out to be unenforceable, the tradesperson claimed quantum meruit for the value of the plumbing work already completed.