GST audit procedure: notice, verification of books, observations, opportunity to reply, and final communication of findings. The rule prescribes that GST audits cover a financial year or multiples and commence by notice in FORM GST ADT-01. A proper officer, assisted by a team, must verify books, returns and documents to assess turnover, exemptions, tax rates, input tax credit and refunds, record observations in audit notes, inform the registrant of discrepancies for a reply, finalize findings after considering the reply, and communicate final findings in FORM GST ADT-02.