The results of your audit should be contained in a formal letter from the Canada Revenue Agency (CRA). It should advise you on the procedure for filing an appeal: the contact information, the time limit by which you must file, and the required documentation. Or, you can contact the CRA’s Business Window at 1-800-959-5525 for assistance.
If you’re in doubt about the findings of the audit, consider this. If you file an appeal, you can always withdraw it – but if you don’t file by the expiry of the time limit, you will be considered to have accepted the audit results.
This is a great example of a case where you should seek expert professional advice on your particular situation. Many accounting and legal practices have tax experts on staff, or can evaluate whether you would benefit from discussing a tax appeal with a specialist.