To develop an internal audit plan that aligns with ISO 9001 standards, focusing on the most critical areas for compliance, follow these steps:

1. **Determine Audit Objectives**: Based on ISO 9000:2015 and ISO 19011:2018, your objectives should include verifying the effective implementation and maintenance of the quality management system, evaluating compliance with documented procedures and legal requirements, and assessing the effectiveness of corrective actions.

2. **Identify Critical Areas**: Focus on the most complex processes and those with a high probability of nonconformities. This includes areas like quality control activities, nonconforming product management, process monitoring, and top management's leadership and commitment.

3. **Develop an Audit Checklist**: Review documented information such as standards, records, and procedures. Determine what evidence you need to see, what questions to ask, and who to speak with. Write down these questions and ensure they cover all requirements of the standard.

4. **Plan the Audit Schedule**: Establish the frequency, methods, responsibilities, and reporting requirements for your internal audits. Consider the results of previous audits and the importance of processes when planning.

5. **Conduct the Audit**: Follow the planned itinerary, using your checklist to guide the audit process. Ensure the objectivity of the audit process and document the results.

6. **Report and Follow-up**: Communicate audit results to relevant management and document them. Follow up on any issues or improvements identified during the audit.

By focusing on these steps, you can ensure your internal audit plan is comprehensive and aligned with ISO 9001 standards.