law: The Central Goods and Services Tax Act, 2017
  Chapter XIII
  Audit
  65. Audit by tax authorities.-
  (1) The Commissioner or any officer authorised by him, by way of a general or a specific order, may undertake audit of any registered person for such period, at such frequency and in such manner as may be prescribed.
  (2) The officers referred to in sub-section (1) may conduct audit at the place of business of the registered person or in their office.
  (3) The registered person shall be informed by way of a notice not less than fifteen working days prior to the conduct of audit in such manner as may be prescribed.
  (4) The audit under sub-section (1) shall be completed within a period of three months from the date of commencement of the audit:
  Provided that where the Commissioner is satisfied that audit in respect of such registered person cannot be completed within three months, he may, for the reasons to be recorded in writing, extend the period by a further period not exceeding six months.
  Explanation.-For the purposes of this sub-section, the expression "commencement of audit" shall mean the date on which the records and other documents, called for by the tax authorities, are made available by the registered person or the actual institution of audit at the place of business, whichever is later.
  (5) During the course of audit, the authorised officer may require the registered person,-
  (i) to afford him the necessary facility to verify the books of account or other documents as he may require;
  (ii) to furnish such information as he may require and render assistance for timely completion of the audit.
  (6) On conclusion of audit, the proper officer shall, within thirty days, inform the registered person, whose records are audited, about the findings, his rights and obligations and the reasons for such findings.
  (7) Where the audit conducted under sub-section (1) results in detection of tax not paid or short paid or erroneously refunded, or input tax credit wrongly availed or utilised, the proper officer may initiate action under section 73 or section 74.