How does your team communicate/justify project delays to the upper management?

I recently took some of the project management responsibilities as the manager of my team left the company.

I obsess over making good estimates. I want to help the team members make better estimates and want any changes, usually delays, to be communicated clearly and understood by the upper management on a regular basis.

Sometimes I feel like I'm the only person obsessing over it, but there are signs at my company that we need clear communication of these. For example, there's a tendency to underestimate, especially for projects that do not seem as difficult as they actually are.

How much does the upper management of your organization care about good estimates, and how well do they work with unexpected changes?

If you have a template for reporting these estimate changes, from individual team members to the team lead/PM, and then the team lead/PM to upper management, can you share it? If not, what do your reports usually look like?