Section 66 explained: this guide covers what it means, who it applies to, the step-by-step process, documents required, fees, due dates and penalties in India — so you can stay compliant with confidence and avoid costly mistakes.
An audit conducted not by the department but by a chartered accountant or cost accountant the department chooses, at the department's expense, with the taxpayer having no say in the appointment.
Section 66(1): if at any stage of scrutiny, inquiry, investigation or any other proceedings before him, an officer not below the rank of Assistant Commissioner, having regard to the nature and complexity of the case and the interest of revenue, is of the opinion that the value has not been correctly declared or the credit availed is not within the normal limits, he may, with the prior approval of the Commissioner, direct the registered person in writing to get his records including books of account examined and audited by a chartered accountant or a cost accountant nominated by the Commissioner. 66(2): the report is due in ninety days, extendable by a further ninety days. 66(5): the Commissioner determines and pays the expenses, and that determination is final.
The four gates
Every one of these must be crossed before a special audit can be directed.
1. A pending proceeding. "At any stage of scrutiny, inquiry, investigation or any other proceedings before him." A special audit cannot be initiated in the abstract; something must already be on foot.
2. Rank. The officer must be not below the rank of Assistant Commissioner.
3. The opinion, on stated considerations. Having regard to the nature and complexity of the case and the interest of revenue, the officer must be of the opinion that either:
- the value has not been correctly declared; or
- the credit availed is not within the normal limits.
Those are the only two grounds. A special audit cannot be directed because turnover is large, because returns were late, or because classification is disputed. The subject matter is confined to valuation and abnormal credit.
4. Prior approval of the Commissioner. Not concurrence afterwards, and not approval by a Joint or Additional Commissioner.
Rule 102(1): the direction under s.66(1) shall be issued in FORM GST ADT-03.
Who conducts it
A chartered accountant or a cost accountant — nominated by the Commissioner.
The taxpayer does not choose, cannot object to the nominee on preference grounds, and does not engage the professional. The relationship is between the Commissioner and the nominee.
That distinguishes s.66 sharply from the GSTR-9C certification regime, where the professional is the taxpayer's own. Here the nominee reports to the Assistant Commissioner, not to the taxpayer.
The ninety days, and the extension
Section 66(2): the nominated accountant shall, within the period of ninety days, submit a report of such audit duly signed and certified by him to the said Assistant Commissioner, mentioning such other particulars as may be specified.
The proviso: the Assistant Commissioner may, on an application made to him by the registered person or the chartered accountant or cost accountant, or for any material and sufficient reason, extend the period by a further period of ninety days.
So the outer limit is one hundred and eighty days, and — unusually — the registered person may apply for the extension. Where the records are voluminous or a genuine reconstruction is needed, that application is worth making rather than allowing an incomplete report to be filed.
Rule 102(2): on conclusion of the special audit, the registered person shall be informed of the findings in FORM GST ADT-04.
Section 66(3): it does not matter that you were audited already
Section 66(3): the provisions of sub-section (1) shall have effect notwithstanding that the accounts of the registered person have been audited under any other provisions of this Act or any other law for the time being in force.
So a statutory audit under the Companies Act, a tax audit under the Income-tax Act, a GSTR-9C reconciliation, or even a completed s.65 departmental audit is no bar. The special audit is additional.
Section 66(4): the hearing
Section 66(4): the registered person shall be given an opportunity of being heard in respect of any material gathered on the basis of the special audit under sub-section (1) which is proposed to be used in any proceedings against him under this Act or the rules.
This is a strong protection, and it is worded around material, not conclusions. Any material gathered in the special audit that the department proposes to use must first be put to the taxpayer with an opportunity to be heard.
The practical consequence: a show cause notice that relies on the special audit report must have been preceded by that opportunity, and the report and its underlying material must have been supplied. A demand built on a special audit report the taxpayer has never seen fails on s.66(4) alone.
Section 66(5): who pays
Section 66(5): the expenses of the examination and audit, including the remuneration of the chartered accountant or cost accountant, shall be determined and paid by the Commissioner, and such determination shall be final.
The taxpayer bears no cost of the special audit itself. It will of course bear the cost of its own advisers in responding, but the nominee's fee is a departmental expense.
What follows
Section 66(6): where the special audit 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 s.73 or s.74 or s.74A.
The words "or section 74A" were inserted by the Finance (No. 2) Act, 2024, notified through Notification No. 17/2024-CT dated 27.09.2024, w.e.f. 01.11.2024 — aligning s.66 with the new unified demand provision for FY 2024-25 onwards.
So again: the ADT-04 is not a demand. Determination happens separately.
Section 65 audit and section 66 special audit compared
| s.65 audit | s.66 special audit | |
|---|---|---|
| Who conducts | Departmental officers | CA or cost accountant nominated by the Commissioner |
| Trigger | Discretionary, any registered person | Pending proceeding + value or abnormal credit concern |
| Authorising rank | Commissioner or authorised officer | Assistant Commissioner, with Commissioner's prior approval |
| Notice / direction | ADT-01, 15 working days | ADT-03 |
| Time | 3 months + 6 months from commencement | 90 days + 90 days for the report |
| Findings | ADT-02 within 30 days | ADT-04 |
| Hearing | Not expressly before findings | Express, s.66(4), on material to be used |
| Cost | Departmental | Commissioner pays, determination final |
Key takeaways
- Special audit needs a pending proceeding, an Assistant Commissioner, the Commissioner's prior approval, and one of only two grounds — value, or abnormal credit.
- The auditor is nominated by the Commissioner, not chosen by the taxpayer.
- ADT-03 directs it; the report is due in ninety days, extendable by ninety on application by either side.
- Findings in ADT-04; a prior statutory, tax or departmental audit is no bar (s.66(3)).
- Section 66(4) requires a hearing on any material proposed to be used against the taxpayer.
- The Commissioner pays the auditor, and that determination is final.
Read next
- Section 65 Audit: ADT-01, the Three Months and the Extension
- Rule 101: How a GST Audit Is Actually Conducted
- Transaction Value and the Sole Consideration Test
- Audit by Tax Authorities Under GST — Section 65 and 66
Disclaimer: Positions stated as on 5 September 2026, based on the CGST Act and Rules as amended to 31 March 2026 (ICAI Bare Law, 12th edition).