The questions of whether and to what degree unjust enrichment occurs in the case of an invalid work contract are complex, and decisions in these cases will depend on various factors. One of the most important considerations is whether the client is the owner of any real estate built under the contract. If the client does not own this real estate, a question will arise about how to calculate the amount of restitution (compensation) payable: Should the compensation reflect the increased value of the real estate after the making of investments, or the value of the work performed under the contract?
In its decision no. 32 Cdo 1063/2016 of August 2, 2016, the Czech Supreme Court found that when a property is not owned by one of the parties to an invalid work contract, there can be no duty to provide restitution for unjust enrichment related to its increased value following investments. Under Art. 457 of Act No. 40/1964 Coll., the Civil Code, each party to an invalid contract must restore all items acquired under the contract to the counterparty; this restitution duty cannot include the value of property that the party does not own. In other words, the party has not been enriched by the increase in value of property belonging to a third person. Rather, it was only enriched by the consideration it received from the other party under the (invalid) contract.