What must auditors document according to professional standards?

Auditors are required to document all findings during the audit to ensure a comprehensive record of the audit process, the evidence collected, and the conclusions reached. This documentation serves as a vital component of the audit trail, allowing future auditors to understand what was analyzed and the basis for the judgments made.

By documenting every finding, auditors provide transparency and accountability. It also helps in facilitating follow-up actions, developing recommendations, and ensuring compliance with regulatory standards. Thorough documentation aids in maintaining professional integrity and supporting the audit's reliability, thus enhancing the overall quality of the audit process. This practice is in line with the professional standards which emphasize thoroughness in documentation to uphold the credibility of the audit findings and conclusions.

The other choices do not encompass the full scope of what auditors must document. Major findings alone, summaries of performance, or details of previous audits do not capture the necessity for a complete and detailed record of all observations made during the audit. Therefore, documenting all findings is essential to adhere to professional standards.