 In these circumstances, a court may order the party making use of the defective or incomplete performance to pay a reduced amount to the party in breach.The onus to prove the amount of the reduction is on the breaching party.The "exceptio non adimpleti contractus" is available in all types of contract, but not where a breach is excused by law, or where the risk of defective performance lies with the party who wishes to raise the "exceptio".