When does a breach of contract occur?

A breach of contract occurs when one party fails to meet their contractual obligations, which includes not delivering goods as promised. This can manifest in various ways, such as not providing the correct quantity, quality, or even failing to deliver at all. In the context of the question, if a party does not deliver the goods that they agreed to provide in the contract, it constitutes a clear violation of the agreement, thereby resulting in a breach.

While underperformance in services or delayed payments can also lead to a breach of contract, the fundamental definition focuses on the failure to meet the specific terms agreed upon, such as the delivery of goods. Hence, the most straightforward and clear-cut example of a breach, according to the options given, is when a party fails to deliver the goods that were promised in the contract.