When solutions already exist, it's recommended to review them regularly to get an overview of the solution's state.
A software audit can have different forms, depending on where is your uncertainty:
An audit is not only a document stating the limitations and/or risks. It's a mission that also provide a report, with recommendations and solutions, adapted to your problem and specificities.
I will provide you a precise evaluation of an application or a system, and give you hints on how to handle the specific problem you're facing.