Time of supply of goods determines tax liability timing: invoice date, payment entry, receipt of goods, or voucher rules apply. Time of supply of goods fixes tax liability by reference to the earlier of invoice issuance or receipt of payment, with supply deemed only to the extent covered by invoice or payment and payment date taken as the earlier of book entry or bank credit. Reverse charge supplies are timed by receipt of goods, recipient's payment entry or bank debit, or a post-invoice period; vouchers by issue or redemption; otherwise timing follows return due date or tax payment. Additions like interest and penalties are timed on receipt by the supplier.