Do you have an Internal Audit Charter? If not, this is something required by the IIA's Standards. I believe the IIA has a sample IA Charter on their website.
Regarding your question on an Internal Audit Policy, mine includes the following topics:
1. Function of Internal Audit
3. Risk Assessment and Internal Audit Plan
4. Communicating Results
5. Quality Assessment and Improvement Program (QAIP)
6. Internal Audit Performance Measures
7. Ethics and Personal Standards
8. Continuing Professional Development
9. Records Retention
I'm sure you can also find examples on the internet; manay universities have this information posted. If you need more specifics, plese feel free to PM me.
"Who would have thought that the thing that would save this company would be work. And pancakes." - Michael Scott-The Office