Audit by tax authorities may require production of records and can trigger tax recovery proceedings if discrepancies are found. Commissioner or authorised officers may audit any registered person with prescribed period, frequency and manner, at business premises or office, after at least fifteen working days' notice. Audit must ordinarily finish within three months, extendable by the Commissioner for up to six months with reasons recorded; commencement is when records are produced or audit begins. Officers may demand access to books, information and assistance. The proper officer must notify findings, reasons and rights within thirty days, and detection of tax shortfall or improper input tax credit may lead to initiation of recovery proceedings.