GST composition levy stock intimation required when migrating from existing law, listing supplier invoices, tax components, and verification. Intimation of details of stock is required when a person registered under the existing law opts to pay tax under the composition levy on the appointed day, with identification data (GSTIN, names, address, ARN and jurisdiction) and schedules for opening stock from registered and unregistered suppliers detailing invoice data, values and tax components, plus tax paid details and a verification by an authorised signatory.