Assessment of unregistered persons enables best judgement GST assessments with prescribed notice, order and summary procedures. Section 63 authorises best judgement assessment of persons liable to register but remaining unregistered, overriding sections 73, 74 and 74A where inconsistent. The proper officer must serve notice in FORM GST ASMT-14 allowing 15 days, pass assessment in FORM GST ASMT-15, serve a summary in FORM GST DRC-01 and upload it in FORM GST DRC-07, giving the taxpayer an opportunity of being heard. The time limit for such orders is subject to a five year bar counted from the date specified under section 44 for filing the annual return. The Deputy or Assistant Commissioner is the proper officer.