Scott, Yes, you can use data (results) from your customer audits as part of the input into your internal audit, but not as your internal audit. Why? Mainly because you (your organization) have no ownership of their audit process which is an absolute for internal audits.
Custumer audits can be used in two ways as input:
First when setting up your internal audit plan. You have to have an internal audit plan that covers all processes. The extend/frequency at which you audit each process depends on the criticallity of the process and the historic performance of the process. Previous customer audits can be used as input for the performance evaluation.
Once you have determined your audit plan, you need to execute the scheduled audits. However, if an customer audit satisfies the needs for your internal audit, for practical reasons you may used the customer audit results in lieu of the internal audit. Following requirements should be considered:
- The scope and criteria referenced in the customer audit should be clearly specified in the customer audit report
- Document your justification why the customer audit satisfies your internal audit need
Especially the audit criteria may differ between your internal and custumer audits
- Internal audits determine whether the quality objectives of your company have been met
- Cusomer audit determine whether you quality system and product satifies your customer's needs and requirements
Be sure these two are alligned when you use customer audits to satisfy your internal audit program.
Lastly, be sure all audit criteria have been covered. You still need to audit the areas/criteria which have not been covered. If you have inadequate internal resource, you may outsource the activity. Be sure that the auditor you hire does understand your objectives with the audit and uses your quality system, including its objectives as reference.