To develop an internal audit plan that aligns with ISO 9001 standards, focusing on the most critical areas for compliance, you can 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 areas with complex processes or high potential for nonconformities. This includes quality control activities, nonconforming product management, process monitoring, and evaluation.

3. **Review Documented Information**: Examine standards, records, procedures, and work instructions to understand the requirements and gather evidence.

4. **Develop Audit Checklist**: Create questions based on the ISO clauses relevant to your organization, such as clauses 8.6, 8.7, 9.1, 9.2, 10.2, and 10.3. Ensure the checklist covers all standard requirements.

5. **Plan the Audit Schedule**: Establish the frequency, methods, responsibilities, and reporting requirements for the audits. Consider the results of previous audits and the importance of processes.

6. **Ensure Auditor Competence**: Make sure your internal auditors are trained and competent, and ensure they do not audit their own work to maintain objectivity.

7. **Communicate and Document Results**: Clearly communicate audit results to relevant management and document the findings for future reference and improvement actions.

By following these steps, you can create an effective internal audit plan that aligns with ISO 9001 standards and focuses on critical compliance areas.