No Waiver Clause

The purpose of a "no waiver" clause is to try to ensure that a party to the contract does not accidentally or informally waive its rights to bring proceedings and recover damages etc under the contract in the event of a breach of the contract by the other party. Such a clause may specify that contractual rights can only be waived by means of a written notice.

For instance:

No breach of any provision of this Agreement will be waived except with the express written consent of the party not in breach.