GSTR-1, explained

GSTR-1 is the return where you report your outward supplies, that is, your sales, for a period. It is how your invoices reach your buyers' GST records.

What it contains

Invoice-level detail of B2B sales, summary of B2C sales, credit and debit notes, and exports.

When it is due

Monthly filers file by the 11th of the next month. Small taxpayers under the QRMP scheme file quarterly. Filing it correctly is what lets your buyers claim input credit.