This document provides a comprehensive overview of the GSTR-1 JSON data format, its architectural requirements, and the strict validation rules necessary for successful submission to the GSTN portal. The GSTN hasn't published an official JSON schema.. So this has been reverse engineered based on validity testing against the official GST website, APIs found online, and the documentation associated with the "GST Offline Tool".
GSTR-1 is a mandatory return for all GST-registered businesses in India, used to report details of all outward supplies (sales).