Scenario 1: If supply, invoice, and payment all happen before 22nd September - then old rate applies.
Scenario 2: If supply is before but invoice and payment are after 22nd September - then the new rate applies.
Scenario 3: If supply and invoice are before but payment is after - the old rate will be applicable.
Scenario 4: If invoice and payment are before but actual supply happens after 22nd September - the old rate applies.
Scenario 5: If supply is after, invoice is before, and payment is after- the new rate applies.