Determination of unpaid tax: notice, time limits and pre-notice payment options can conclude GST proceedings. Determination of unpaid or short paid tax, erroneous refund or wrongly availed input tax credit for Financial Year 2024-25 onward requires issuance of a show cause notice within prescribed limitation periods, allows service of a deemed notice by statement for other periods with identical grounds, and mandates the proper officer to determine tax, interest and penalty and issue an order within a specified period with limited extension. The section prescribes different penalty consequences for non-fraudulent and fraudulent or wilful misstatement cases, provides pre-notice and post-notice payment options that may conclude proceedings, and permits issuance of notice for any shortfall in self-payment.