Change in rate of tax: time of supply fixed by priority between invoice date and payment receipt following rate change. Determination of time of supply on change in tax rate prioritises invoice date and receipt of payment depending on whether supply occurred before or after the rate change: where both invoice and payment occur after the change the earlier governs; invoice before/payment after yields invoice date; payment before/invoice after yields payment date; complementary rules apply when supply is after the change. Receipt of payment is treated as bank credit date if credit occurs more than four working days after the rate change, and generally means the earlier of book entry and bank credit.