IDW PS 951

Audit standard for the internal control sy

The audit of the internal control system at the service company for functions outsourced to the service company

The auditing standard IDW PS 951 specifies requirements for auditing the ICS of a service company. The focus of an audit in accordance with IDW PS 951 is the ICS of the company to be audited and relevant processes. A description of the ICS by the company to be audited is a component of the reporting. IDW PS 951 supports compliance with legal and regulatory requirements for companies in Germany. An audit in this regard is based on the description of the internal control system and the statement issued by the legal representatives.


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An inspection according to IDW PS 951 can include two dimensions

  • Typ 1

    Assessing the adequacy and design of controls at a predetermined point in time without making a statement about their effectiveness.

  • Typ 2

    In addition to Type I, an assessment of the effectiveness of the established controls of the ICS is carried out within a predefined audit period.

Benefits of a certification according to IDW PS 951:

  • Proof of the adequacy and possible effectiveness of the service-related ICS

  • Assessment of outsourcing risks for a service company

  • Reporting on the ICS or its certification

  • Quality feature compared to non-certified companies

  • Marketing instrument for maintaining or expanding the customer base

A possible project flow is shown in the following workflow.
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