UIN holders must file Form GSTR-11 monthly reporting inward supplies for consumption or use and certify the details. Form GSTR-11 requires UIN holders to furnish a monthly inward supplies statement for consumption or use, capturing supplier GSTIN, invoice details, supplier name, HSN/SAC, taxable value and tax components (IGST, CGST, SGST); the form is to be auto-populated where possible, allows addition of missed invoices, and must be certified by an authorized signatory and filed by the 28th day of the following month.