In the "Define IT Universe" stage of the IT audit plan development process, the primary action is to identify significant applications that support the business operations. This step involves mapping out the IT environment, including key systems, applications, and infrastructure components that are critical to achieving business objectives. By identifying these significant applications, auditors can focus on areas that have the greatest impact on the organization's performance and risk profile. This stage sets the groundwork for subsequent steps such as risk assessment, ranking subjects, and selecting audit engagements.
IIA Global Technology Audit Guide (GTAG): "Developing the IT Audit Plan" ISACA's COBIT Framework for IT Governance and Management

The planning phase is crucial for any audit engagement and must be completed and approved before starting fieldwork. This ensures that the engagement has a clear scope, objectives, and methodology, which are necessary for conducting an effective and efficient audit. Without proper planning, the audit team may miss critical areas or waste resources on low-priority risks.
IIA Reference:
IIA Standard 2200: Engagement Planning requires that internal auditors develop and document a plan for each engagement, including the engagement's objectives, scope, timing, and resource allocations, before starting fieldwork.
The Practice Guide on Planning emphasizes that completing and approving the planning phase ensures that all necessary preparations are made, and potential risks are identified and mitigated before fieldwork begins.

An engagement work program is of greatest value to audit management when it helps ensure the achievement of the engagement objectives. The work program outlines the audit procedures and tests that need to be performed to gather sufficient and appropriate evidence to support the audit findings and conclusions. By aligning the work program with the engagement objectives, auditors can focus their efforts on the most critical areas, ensure that all necessary steps are taken, and ultimately achieve the intended outcomes of the audit.
Reference:
Institute of Internal Auditors (IIA), International Standards for the Professional Practice of Internal Auditing (Standards), Standard 2240 - Engagement Work Program.

In the "Define IT Universe" stage of the IT audit plan development process, the primary action is to identify significant applications that support the business operations. This step involves mapping out the IT environment, including key systems, applications, and infrastructure components that are critical to achieving business objectives. By identifying these significant applications, auditors can focus on areas that have the greatest impact on the organization's performance and risk profile. This stage sets the groundwork for subsequent steps such as risk assessment, ranking subjects, and selecting audit engagements.
Reference:
IIA Global Technology Audit Guide (GTAG): "Developing the IT Audit Plan" ISACA's COBIT Framework for IT Governance and Management