Arm's Length Principle Audit and its Duration

I have a business, and I hear that the tax authority can assign an audit regarding compliance with the arm's length principle. I am very concerned about how long such an audit can last, when they generally have the right to initiate it, and whether they can extend it without my consent. If the audit is already ongoing for the maximum possible term, what are the legal grounds for its extension by the tax authority, and how can I protect my interests to prevent violations by the tax authorities?