Time of supply on change in tax rate determined by sequencing of invoice issuance and payment receipt. Determination of time of supply on change of tax rate depends on relative timing of invoice issuance and payment receipt. For supplies before the change, the earlier of invoice date or payment date governs depending on which occurred before or after the change; payment entered in books or bank credit is the date of receipt. For supplies after the change, analogous rules assign time of supply to payment or invoice date according to their sequencing, with a proviso treating bank credit as receipt only when credited after four working days from the rate change.