Time of supply on tax rate change: invoice and payment timing determine the tax point and applicable rate. When GST rate changes, the time of supply is determined by invoice and payment timing relative to the rate-change date: for supplies before the change, the earlier of payment receipt or invoice date applies where both occur after the change; invoice date applies if issued before and payment after; payment date applies if received before and invoice after. For supplies after the change, payment date applies if received after but invoice before; earlier of payment or invoice if both before; invoice date if issued after but payment before. Bank credit counts as receipt only if credited after four working days; receipt means accounting entry or bank credit, whichever is earlier.