How much would like to make per hour or per year, based on your previous salary and your skills? As an independent contractor, you should consider charging at least 50% more than what you would make as a salaried employee and up to double the amount, because you have additional taxes to pay, additional expenses, no benefits, and you do not always work 40 hours per week because work isn't always steady, you have to do marketing, write proposals, etc. Based on the number you come up with, you can determine what a per-report fee should be based on your experience and how long it takes to audit a report. Most providers would rather pay you a per-report fee than an hourly rate because it's more predictable for them. They don't want to pay extra money if you take longer than expected. Of course, you want to charge a rate that reflects the complexity of the reports you need to audit, so you don't end up eating time.
For example, if you earned $50,000 as a salaried employee, that equates to $25/hour (50,000 / 2000). So your hourly rate as an independent contractor would be $37 to $50 per hour. If you audit 4 reports per hour that would be $9.25 to $12.50 per report. If your fee is too high, they will tell you, but you don't want to leave $ on the table either.
I hope that gives you a starting point.
