The correct answer is Documenting findings, outcomes, and lessons learned because proper documentation and closure are the final steps in the ticket management and troubleshooting process. According to CompTIA Network+ (N10-009) objectives under network operations and troubleshooting methodology, once an issue is resolved, technicians must verify full system functionality, implement preventive measures if needed, and document the entire process before closing the ticket.

Documentation ensures that all relevant information—such as the root cause, corrective actions taken, configuration changes made, and lessons learned—is recorded for future reference. This supports knowledge base updates, trend analysis, compliance requirements, and improved response times for similar incidents.

Escalation (Option A) occurs earlier if the issue cannot be resolved at the current support tier. Establishing an action plan (Option D) is part of the remediation phase, not the final step. Functional and non-functional testing (Option B) occurs during verification before closure.

Therefore, comprehensive documentation and formal ticket closure represent the final step in the ticket management lifecycle.