Special audit power requires records to be audited when declared value or input tax credit appears unreliable, enabling enforcement action. Section 66 enables an Assistant Commissioner, with the Commissioner's approval, to direct a registered person to have records audited by a chartered or cost accountant nominated by the Commissioner when declared value or input tax credit appears incorrect; the nominated accountant must submit a signed audit report within ninety days (extendable for cause). The registered person must be heard before material from the special audit is used in proceedings; the Commissioner determines and pays the audit expenses. Detection of tax shortfall, erroneous refund or wrongly availed input tax credit may lead to action under the Act.