# SA 600: Key Definitions
SA 600 "Using the Work of Another Auditor" governs situations where the auditor reporting on an entity's financial statements relies on audit work done by a different auditor for one or more components of that entity.
## The Three Core Definitions
### Principal Auditor (PA)
The auditor responsible for reporting on the financial information of the entity as a whole, even when that information includes components audited by another auditor.
> The PA signs the main audit report and bears ultimate responsibility for it.
### Other Auditor (OA)
An auditor other than the principal auditor who is responsible for reporting on the financial information of a component. The OA's findings feed into the PA's overall conclusions.
### Component
Any division, branch, subsidiary, joint venture, associated enterprise, or other entity whose financial information is included in the financial statements audited by the principal auditor.
## Why This Standard Exists
When a company has branches or subsidiaries audited by different auditors, two problems arise:
1. Role clarity — Who is responsible for what?
2. Coordination — How do the two auditors work together effectively?
SA 600 resolves both by requiring the principal auditor to follow specific procedures when relying on another auditor's work.