Suspension of GST registration requires a 30-day portal reply; officer may revoke suspension or proceed to cancellation. Suspension under sub-rule (2A) of rule 21A is triggered by significant discrepancies in return comparisons indicating contravention and revenue risk. A system intimation/notice (FORM GST REG-31 or interim FORM GST REG-17 on dashboard) states reasons and requires the taxpayer to reply within thirty days in FORM GST REG-18 via the portal, including filing overdue returns or meeting specified requirements. The proper officer, after review or on expiry of the reply period, may revoke suspension by FORM GST REG-20 or cancel registration by FORM GST REG-19; nodal officers receive lists for action.