Who is required to furnish the details of outward taxable supply? In what format should such details be furnished? What is the due date for furnishing such details?

All registered taxable persons are required to furnish the details of outward supplies of goods and services effected during the tax period, except:
(a) Input Service Distributors

(b) Composition suppliers

(c) Non-resident taxable persons

(d) Persons liable to deduct tax at source as per Section 51

(e) Persons liable to collect tax at source as per Section 52

(f) Person providing OIDAR Services

The details should be furnished electronically in the format prescribed in
FORM GSTR-1. Such returns should be furnished on or before 10th of the succeeding tax period.

(ICAI FAQ PUBLICATION 06-09-2017 -: Returns : FAQ NO. 2)