Time of supply rules determine when GST liability arises, prioritising invoice issuance or recorded receipt of payment. The provision fixes the Time of Supply of goods as the earlier of invoice issuance (or the last date to issue it) and the date payment is received or recorded, with supply deemed to the extent covered by invoice or payment and receipt defined as entry in books or bank credit. For reverse charge transactions the time is the earliest of goods receipt, recipient's payment entry or debit, or thirty days after the supplier's invoice, with voucher supplies timed to issue or redemption and unresolved cases timed to return filing or tax payment; additions are timed to receipt.