cash discount treatment under gst

in case of cash discount the value of supply will be determined in accordance with section 15(3)
in clause (a) cash discount should be shown in the invoice before the supply is made
(b)in case cash discount is made after supply is made it should relate to an agreement made on or before the supply
in case of clause (b) credit note will be issued by supplier and the credit availed by recepient should be reversed