The amount collected by the ecommerce operator (‘operator’,) is to be paid to the credit of appropriate government within 10 days after the end of the month in which amount was so collected. The operator is required to file a return in Form GSTR-8 online giving details of all amounts collected by him for the outward supplies made through his portal, within 10 days of the end of the calendar month to which such statement pertains. The return should contain the names of the actual supplier(s), details of respective supplies made by them and the amount collected on their behalf.
(ICAI FAQ PUBLICATIONS 06-09-2017 TAX PAYMENTS, INTEREST, PENALTIES AND OTHER AMOUNTS: FAQ NO. 59)