Audit powers permit assessment of registered persons with notice, record access, and possible follow-up tax proceedings. Audit powers authorize the Commissioner or an authorized officer to examine any registered person with prior notice, at the business premises or office, and require access to books and information. The audit must be completed within three months from the commencement of audit, extendable for reasons in writing up to six months. On conclusion the proper officer must inform the taxpayer of findings, rights, obligations and reasons within thirty days, and detection of tax discrepancies may trigger statutory tax proceedings.