GST rule amendment extends filing timelines, mandates ITC 01 declaration and prescribes reversal of customs duty credit on imported gold dore bar. The amendment extends the period in rule 3(4) to ninety days; allows UIN grant under rule 17 on the form or after Ministry of External Affairs recommendation; requires an eligible registered person to file FORM GST ITC 01 electronically within thirty days of eligibility (subject to Commissioner's extension); prescribes in new rule 44A that Central tax credit attributable to additional customs duty on imported gold dore bar is restricted to one sixth with five sixths debited at supply or within one week if supply already occurred; and updates appointment, payment, and form provisions including REG 13 and TRAN 1.