GSTR 1 return is used to upload your sales data to the GSTN portal. Every taxpayer needs to report things like invoice summary (Types of Invoices, Credit Notes, Advance Receipts, etc), a summary of documents issued (Documents such as invoices, credit notes, and their serial numbers), a summary of HSN/SAC, etc. These API helps you to get invoices summary and save, submit, and file GSTR-1 form.