Depending on the circumstances, default may not be required. Default is required to be able to dissolve the contract or claim damages, for example.
After expiry of the reasonable period – mentioned in the letter – the debtor is in default. A notice of default gives this party another opportunity to (properly) comply within a reasonable period. Unfortunately, it happens often enough that a contracting party fails to fulfil its obligations, or fails to do so on time or properly.
