Start with ISO 9000:2015, the standard with useful vocabulary for management systems. What is an audit program? A set of one or more audits planned for a given period of time.
Certification bodies expect that every part of an environmental management system (EMS) is audited yearly. So, the period of time is one year. And in that one year, you want to audit all parts of your EMS. Now, how many internal auditors do you have? What is their experience? More experienced auditors are able to perform internal audits with wider scopes without losing quality, and without losing too much time during preparation (you must consider that they are not professionals and have their normal work to do).
Will auditors work together as an audit team or individually? Consider that while thinking about the number of internal audits per year.
Now, about the content of each audit, think about auditing:
· top management
· EMS’s responsible
· Human resources
If there are areas with more nonconformities in the past, think about auditing them more than once in the same year for a better monitorization of the evolution.