Tax determination under section 74A sets notice limits, penalty tiers, and payment options for unpaid GST input credit issues. Section 74A establishes a special mechanism for determining tax not paid, short paid, erroneously refunded, or input tax credit wrongly availed or utilised for financial years 2024-25 onwards. It sets notice limits, time limits, penalty rates for non-fraud and fraud cases, and pre-notice and post-notice payment options with corresponding consequences. It also provides for determination of tax, interest and penalty by order, an extension mechanism, and clarifies the meaning of suppression and the scope of concluded proceedings.