Determination of unpaid tax: extended limitation period and pre-notice settlement options reduce penalties and streamline assessments. Section 74A prescribes procedure for assessing tax not paid, short paid, erroneously refunded or wrongly availed input tax credit for Financial Year 2024-25 onwards: the proper officer issues a show cause notice (threshold excluded), within forty two months of return due date or erroneous refund, may serve related statements deemed to be notices if based on the same grounds, and must pass an order within twelve months (extendable up to six months) determining tax, interest and penalty. The section sets differentiated penalty rates for fraud versus non fraud, provides voluntary pre notice and post notice settlement windows, and specifies that concluded proceedings exclude certain penal proceedings.