When does the liability to pay GST arise in respect of supply of goods and Services?

Section12 & 13 of the CGST/SGST Act provides for time of supply of goods. The time of supply of goods shall be the earlier of the following namely,

(i) the date of issue of invoice by the supplier or the last date on which he is required under Section 31, to issue the invoice with respect to the supply; or
(ii) the date on which the supplier receives the payment with respect to the supply.