Article 523. Unilateral waiver of performance of a contract of delivery

1. Unilateral waiver or modification of a contract of delivery (in whole or in part) is permissible in the event of a fundamental breach of a contract by one of the parties (see para. 4 above). 2. Violation of the contract of supply by the supplier is presumed to be material in cases: delivery of goods of inadequate quality with defects which cannot be eliminated 3. Violation of the buyer ' s contract of delivery is deemed to be substantial in cases: repeated violation of payment deadlines 4. The contract of delivery shall be deemed to have been modified or terminated upon receipt by one party of a notification by the other party of a unilateral waiver. If the contract is to be avoided or modified in whole or in part, unless the notice or agreement of the parties provides for a different period of avoidance or modification of the contract.