Time of supply of goods determines tax liability timing; invoice date or payment receipt controls tax trigger. Time of supply is the earlier of invoice issue (or last date to issue it) and the date payment is received, with payment deemed received on entry in books or bank credit, and where indeterminate the return filing date or date of tax payment governs. For reverse charge supplies the earliest of receipt of goods, recipient's payment entry/credit date, or the date after thirty days from supplier's invoice applies; for vouchers the issue date if identifiable otherwise redemption date. Additions by interest, late fee or penalty are taxable when received by the supplier.