GSTR-1 vs GSTR-3B: What to File and When

GSTR-1 is the return of outward supplies. You declare every B2B and B2C invoice issued in the month, plus credit/debit notes and advances. Filing is due by the 11th of the following month. GSTR-3B is the summary return. You self-assess output tax, claim input tax credit (subject to the GSTR-2B reconciliation), and pay the balance by the 20th of the following month. For most regular taxpayers, the cycle is GSTR-1 on the 11th, GSTR-2B auto-generated on the 14th, GSTR-3B with payment on the 20th, and GSTR-9 (annual return) by December 31.