Every book you read on auditing will list some common and some unique reasons as justifications for audits. What this boils down to is there are a number of reasons one can cite for an audit (read Purpose).
Products are fit for use .
Adequate written procedures exist and are being followed.
Conformance to specification.
Determine effectiveness of use of company resources.
Identify and reduce risks.
These are just a few of the often cited reasons for audits. I m sure, with a little imagination, you, too, can come up with some excellent reasons for audits.
More Reasons For Audits
ISO 9001 Requires Them (QS-9000 4.17 and ISO 9001:2000 8.2.2)
A Control Mechanism Used By Management
Tool For Continuous Improvement
Correct Nonconformities In Systems
Helps Assure Ongoing Systems Operate As Intended And Required
ISO 19011 - Quality and Environmental Management Systems Auditing Forum Discussions