A contract is binding upon all its parties regardless of its form. The binding nature of contracts can be regarded as the cornerstone of contract law and of the entire judicial system.
The party making the offer is bound by the offer as soon as the offer has been received by the recipient. The same rule applies to the acceptance of the offer. If the acceptance is conditional, i.e. the offer is not accepted in its original form, the conditional acceptance is regarded as a new offer. An offer or acceptance may be withdrawn as long as it has not been received by the other party.
A contract can be effective until further notice or for a fixed term. A contract that is effective until further notice remains effective until the party terminates the contract. A termination notice period should be defined in the contract. A fixed-term contract is effective until the end of its term. A contract can also expire when both parties have fulfilled their obligations under the contract.
If one of the contracting parties fails to fulfill the contract, the court and execution authorities may enforce the performance of the contract. Circumstances may change during the lifetime of the contract, but this does not affect the validity of the contract. In all cases, a party to the contract cannot be forced to fulfill the contract or forcing the performance may not be appropriate. In these cases the defaulting party can be held liable for damages for breach of contract.
Contracts cannot be altered unilaterally, but the parties may agree in the contract conditions permitting changes to the contract.