Indirect Tax Laws · Assessment and Audit

Special Audit under Section 66 of the CGST Act (Rule 102)

Updated 5 October 2026 · Fact-checked

Special audit is an audit of a registered person's books by a chartered or cost accountant nominated by the Commissioner. An officer of Assistant Commissioner rank or above, with the Commissioner's prior approval, orders it in complex cases where value is wrongly declared or credit is abnormal. The report is due in 90 days, extendable by 90. The Commissioner pays.

Understand Special Audit

Normal scrutiny, audit and investigation are done by tax officers. Sometimes the books are too complex for an officer to check quickly. Examples are large turnover, many related-party deals, or credit that looks far too high. Special audit solves this by bringing in an outside professional.

Under section 66, an officer not below the rank of Assistant Commissioner can order it. He must be handling a scrutiny, inquiry, investigation or other proceeding. He must also believe, considering the nature and complexity of the case and the interest of revenue, that either the value has not been correctly declared or the credit availed is not within normal limits. He needs the prior approval of the Commissioner. He then directs the registered person in writing, in FORM GST ADT-03 under Rule 102, to get the records, including books of account, examined and audited.

The auditor is a chartered accountant or cost accountant nominated by the Commissioner. The taxpayer does not choose the auditor. The auditor must submit a signed and certified report to the Assistant Commissioner who gave the direction within 90 days. On an application by the registered person or the auditor, or for any material and sufficient reason, that Assistant Commissioner may extend this by a further 90 days. The extension is discretionary, not automatic. The maximum is therefore 180 days.

The cost is not on the taxpayer. The expenses of the audit, including the auditor's remuneration, are determined and paid by the Commissioner. The taxpayer must still cooperate and give access to records.

The taxpayer gets a hearing on any material gathered from the special audit that the department proposes to use against him. The section applies even if the accounts were already audited under section 35(5) or any other law.

Do not confuse this with section 65 audit. Under section 65, the audit is done by officers authorised by the Commissioner, or by the CAG or a chartered accountant or cost accountant nominated by the Commissioner. The main differences from section 66 are the trigger, the approval and the time limit. Section 65 is a periodic or general audit of a registered person. Section 66 needs a pending proceeding, a complex case with revenue interest, doubt on value or credit, and the Commissioner's prior approval. Section 66 also has the fixed report period of 90 days, extendable by 90 days.

Key rules to remember

Who can direct: Officer ≥ Assistant Commissioner + prior approval of Commissioner; A Superintendent or Inspector cannot order special audit. The direction is in writing, in FORM GST ADT-03 under Rule 102.
Grounds: Nature and complexity of case + interest of revenue + (value not correctly declared OR credit not within normal limits); The officer must be in the middle of scrutiny, inquiry, investigation or another proceeding. The grounds are alternative, not cumulative.
Who audits: Chartered accountant or cost accountant nominated by the Commissioner; The taxpayer cannot choose the auditor. The Commissioner nominates.
Time limit: 90 days + possible extension of 90 days = maximum 180 days; The Assistant Commissioner may extend, in his discretion, on application by the registered person or the auditor, or for material and sufficient reason. Extension is not automatic.
Fees and expenses: Determined and paid by the Commissioner; The registered person does not bear the cost, including the auditor's remuneration.
Safeguard: Opportunity of being heard before using material from special audit; Natural justice applies. The section works irrespective of any earlier audit under section 35(5) or other law.

How to solve Special Audit questions

Use this order for any question on special audit. It matches the provision-facts-conclusion style examiners expect.

1Identify the stage: check that the officer is conducting scrutiny, inquiry, investigation or another proceeding.
2Check the rank of the officer: he must be Assistant Commissioner or above. Check that the Commissioner's prior approval was taken and that the direction is in FORM GST ADT-03 (Rule 102).
3Test the ground: is the value not correctly declared, or is credit availed beyond normal limits? Also see whether the case is complex and revenue interest is involved.
4Check the auditor: nominated by the Commissioner, and must be a chartered accountant or cost accountant.
5Check the timeline: report within 90 days, which the Assistant Commissioner may extend by 90 days on application or for material and sufficient reason. Count from the date of direction. The maximum is 180 days.
6Settle the cost: the Commissioner determines and pays the expenses and remuneration. The taxpayer pays nothing for the audit.
7Add the safeguards: the taxpayer must get a hearing on material to be used, and earlier audits do not bar special audit.
8State the conclusion clearly: valid or invalid direction, and what the taxpayer or officer should do.

Quickest way: R-A-N-T-F check

When to use it: Use when a short case asks whether a special audit direction is valid or who bears what.

R: Reason. Is it value wrongly declared or credit beyond normal limits, in a complex case?
A: Approval and Authority. Officer is Assistant Commissioner or above, with the Commissioner's prior approval.
N: Nominee. Chartered or cost accountant nominated by the Commissioner.
T: Time. 90 days, plus a discretionary extension of 90 days.
F: Fees. Paid by the Commissioner, and the taxpayer is heard before use of the findings.
Write one line for each letter, apply to the facts, then conclude.

Common mistakes in Special Audit

Saying the registered person appoints the auditor and pays the fees.
Students link it with statutory audit, where the company appoints and pays the auditor.
Fix: Remember that in special audit the Commissioner nominates the auditor and determines and pays the expenses and remuneration.
Allowing a Superintendent or any proper officer to order it.
Students assume any officer handling the case can order any audit.
Fix: Write that the officer must be not below the rank of Assistant Commissioner, and that the Commissioner's prior approval is needed.
Stating the time limit as 90 days only, or as 180 days flat.
The extension rule is forgotten, or students think 180 days is automatic.
Fix: The base period is 90 days. The Assistant Commissioner may extend it by a further 90 days on application or for material and sufficient reason. The maximum is 180 days.
Mixing up section 65 audit and section 66 special audit.
Both are audits and both come under Assessment and Audit.
Fix: Section 65 audit is done by officers authorised by the Commissioner, or by the CAG or a chartered or cost accountant nominated by the Commissioner. It is a periodic or general audit. Section 66 special audit needs a pending proceeding, a complex case with revenue interest, doubt on value or credit, and the Commissioner's prior approval. Its report period is 90 days, extendable by 90 days.
Saying special audit is barred because accounts were already audited.
Students treat the earlier audit as final.
Fix: The section applies irrespective of an audit under section 35(5) or under any other law.
Ignoring the hearing before using the findings.
Students focus on the report and forget natural justice.
Fix: Add that the registered person must be given an opportunity of being heard on any material gathered from the special audit and proposed to be used against him.

Worked examples

Example 1

Rao Traders is under scrutiny. The Superintendent handling the case finds that input tax credit claimed is far above normal levels and directs Rao Traders to get its books audited by a chartered accountant chosen by Rao Traders, at its own cost. Examine the validity of the direction.

Show the solution

Provision: Special audit under section 66 (Rule 102) may be ordered where credit availed is not within normal limits, during scrutiny or other proceedings.
Authority: The direction must come from an officer not below Assistant Commissioner, with the Commissioner's prior approval. Here a Superintendent has issued it, so it is invalid on authority.
Auditor: The auditor must be a chartered or cost accountant nominated by the Commissioner. Rao Traders cannot choose its own auditor.
Cost: The Commissioner determines and pays the expenses and remuneration. The direction to bear cost is contrary to the section.
Conclusion: The direction is defective on three counts.

Answer: The direction is invalid. The officer lacks the required rank and approval, the auditor must be nominated by the Commissioner, and the cost must be paid by the Commissioner, not Rao Traders. The ground, abnormal credit, is a valid ground, so a correct direction by an Assistant Commissioner or above with approval could be issued.

Example 2

An Assistant Commissioner, with the Commissioner's prior approval, directs Mehta Industries to undergo special audit in a complex case of suspected undervaluation. A cost accountant nominated by the Commissioner is unable to finish in 90 days because of voluminous records and applies for more time. Later, the officer proposes to use the audit findings in a demand proceeding. Advise on the time limit, the extension and the use of the findings.

Show the solution

Ground: Value not correctly declared in a complex case is a valid ground. Authority and approval are in order.
Auditor: A cost accountant is eligible, and he is nominated by the Commissioner.
Time: The report is due within 90 days. The auditor has applied for more time. The Assistant Commissioner who gave the direction may extend by a further 90 days if satisfied on the application, or for material and sufficient reason. The extension is discretionary, and the total cannot exceed 180 days.
Fees: The Commissioner determines and pays the expenses and remuneration. Mehta Industries does not pay for the audit.
Use of findings: Before using any material from the report in the proceeding, the officer must give Mehta Industries an opportunity of being heard.
Conclusion: The period may be extended by up to 90 days, subject to the 180-day maximum, and the findings can be used only after a hearing.

Answer: The Assistant Commissioner may extend the period by a further 90 days, if he accepts the auditor's application, so the report can then be submitted within 180 days in total. The extension is not automatic. The Commissioner bears the cost. The findings may be used in the demand proceeding only after Mehta Industries is heard on the material proposed to be used.

Exam tips

Cover the five points in order: authority and approval, ground, nominee auditor, timeline, and fees. Most case questions test a mismatch in one of these.
In a case MCQ, look for the trap: a wrong officer rank, an auditor chosen by the taxpayer, or the taxpayer paying fees.
For comparison questions, write a two-column difference between section 65 and section 66: who audits, trigger, approval, who pays.
Quote the numbers exactly: 90 days plus a possible 90 days. Do not say 180 days is granted automatically.
End every answer with a clear conclusion that names the valid or invalid parts of the direction.

Practice questions from Assessment and Audit

Special Audit in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Special Audit: frequently asked questions

Who pays the fees for special audit under GST?

The Commissioner determines and pays the expenses of the audit, including the remuneration of the chartered or cost accountant. The registered person does not bear this cost. He must, however, give access to his records.

What is the time limit for the special audit report under section 66?

The nominated chartered or cost accountant must submit the report within 90 days. The Assistant Commissioner may extend it by a further 90 days on an application by the registered person or the auditor, or for material and sufficient reason. The extension is discretionary, and the maximum is 180 days.

What is the difference between section 65 audit and section 66 special audit?

Section 65 audit is conducted by officers authorised by the Commissioner, or by the CAG or a chartered or cost accountant nominated by the Commissioner. It is a periodic or general audit. Section 66 special audit needs an officer of Assistant Commissioner rank or above, with the Commissioner's prior approval, who finds a complex case with wrong value or abnormal credit during a proceeding. Its report is due in 90 days, extendable by 90 days, and the Commissioner bears the cost.

Can a taxpayer who has already had a statutory audit be subjected to special audit?

Yes. The section applies irrespective of whether the accounts were audited under section 35(5) or under any other law. An earlier audit is not a defence.

Does the taxpayer get a chance to respond to the special audit findings?

Yes. The registered person must be given an opportunity of being heard on any material gathered from the special audit that is proposed to be used against him in the proceedings.