GST monthly return Form GSTR-3 finalises outward and inward supplies with tax payment, ITC reconciliation and ledger entries. Form GSTR-3 is a monthly return consolidating outward and inward supplies, rate wise taxable values and IGST/CGST/SGST liabilities, with revisions to invoices and auto population from GSTR 1/GSTR 2. It records ITC availability and reversals, tax on reverse charge supplies, TDS/TCS credits, payments from cash and credit ledgers, and refunds claimed from the cash ledger, culminating in an authorised declaration and prescribed filing timeline.