A supplier removes goods for delivery on 5 April; under section 31 that was the last date for issuing the tax invoice. The goods reach the buyer on 8 April, the invoice is issued late on 10 April,…

Section 12(2)(a) of the CGST Act fixes the time of supply of goods at the earlier of the date of issue of the invoice and the last date on which section 31 required it to be issued. That last date, the date of removal, was 5 April, which is earlier than the late invoice of 10 April and the payment of 20 April; the date the goods reach the buyer plays no part.