The communication plan is an important part of incident response, as it outlines how and when information about the incident should be shared with external entities.
A communication plan is a set of procedures and protocols that define how an organization should communicate with external entities during times of emergency or security incident. The plan typically outlines how and when information about the incident should be shared, and ensures that any relevant stakeholders are informed of the incident in a timely manner. It also serves as a guide for determining what information to share with outside parties. Here is a link to an article from CompTIA's website about the importance of a communication plan for incident response for your reference: https://www.comptia.org/content/incident-response-communication-plan