Exchange rate and input tax credit rules updated under GST, affecting valuation, ITC declarations and credit reversal mechanics. Amendments revise timelines, form content and valuation rules under Punjab GST: exchange rates for goods follow Customs Board notifications and for services follow generally accepted accounting principles; electronic declaration in FORM GST ITC-01 is required to claim input tax credit with separate treatment for different tax components; reversal of credit on additional customs duty for imported gold dore bar restricts immediately available credit to one-sixth with the balance debited on supply or within a transitional period; procedural and form changes clarify invoicing, UIN registration and return generation rules.