HSNS Cess declaration: online filing mandates Form HSNS DEC 01 with process/machine details, documents, verification and submission lock. Filing Form HSNS DEC 01 on the CBIC HSNS portal requires taxpayers to select category (machine based or manual), enter auto fetched basic details, list specified goods and brands, save row entries, upload up to five PDFs (max 2MB each), provide detailed machine or manual process particulars as applicable, furnish an authorised signatory verification acknowledging penal liability, and submit to obtain a declaration number; submitted declarations are immutable and no fresh declaration may be filed while a prior declaration is pending approval.