If at all your are eligible for GST Audit procedure, it is always advisable to contact a Chartered Accountant for such complex procedure because they have the expertise and practical experience due to which they would definitely avoid any error or future penalties. Apart from this, if one wants to prepare GST audit report by themselves, then we have GST online portal www.gst.gov.in. After logging in, one can take the route of Return dashboard, Annual return tab and proceed. One may always take help of online websites and carefully progress with each step. But it goes without saying that at the end the GST Audit report requires authentication by a Chartered Accountant or a Cost & Work Accountant and there the charges will be more or the same because a CA or CWA will thoroughly examine your work and then will certify the same. Always remember to not to get involved in shortcut method of procuring signature of a professional on a document which is actually prepared by any non-professional person. On the same note, it is the best practice of ethics to first examine any document to the fullest of its facts and correctness and then authenticate the same because certifying a certain document will bear responsibilities and consequences too.