According to the Project Management Professional (PMP) principles, transparency and active communication with stakeholders, including customers, are key to effective project management. When unexpected issues arise that may impact the project’s timeline or cost, it is the project manager’s responsibility to inform the customer and discuss potential solutions. This allows the customer to make informed decisions about whether they prefer to adjust the timeline or allocate additional resources (and thus increase the cost) to keep the project on schedule. References: Project Management Professional (PMP) Certification Handbook, PMBOK Guide (6th Edition), Chapter 10: Project Communication Management. Professional in Business Analysis (PMI-PBA) Handbook, Chapter 5: Stakeholder Engagement.