Most corporations only require a simple Notice to Reader to be produced at their year end. The NTR is accompanied by a notation on the scope and limitations of the reports which will state that a review or audit was not preformed.
As with anything you are getting what you paid for. Check out the references and experience of the firm that you are hiring.
For smaller businesses, hiring a bookkeeper to do your NTR versus a certified accountant can save you quite a bit of money, but do realize that you are in the end accountable for the accuracy of the reporting. This is the case for whomever does the reports, certified or not, so be sure you are using someone that you trust.
Have a great day!