Audit by tax authorities: statutory rules set notice, verification powers, time limits and referral for assessment action. Audit by tax authorities empowers the Commissioner or an authorised officer to audit any registered person in prescribed manner, at business premises or office, after giving notice not less than fifteen working days. Audits must be completed within three months, subject to a written extension up to six months; commencement is tied to availability of records or institution of audit. Officers may verify books, require information and assistance. After audit the proper officer must notify findings, rights, obligations and reasons within thirty days, and detection of tax discrepancies may trigger statutory assessment action.