Section 31(3)(g) in The Goa Goods and Services Tax Act, 2017
(g)a registered person who is liable to pay tax under sub-section (3) or sub-section (4) of section 9 shall issue a payment voucher at the time of making payment to the supplier. (4) In case of continuous supply of goods, where successive statements of accounts or successive payments are involved, the invoice shall be issued before or at the time each such statement is issued or, as the case may be, each such payment is received.