Input tax credit discrepancy may trigger portal intimation requiring payment with interest or an explanation within a statutory period. Rule 88D requires electronic intimation when ITC claimed in return exceeds auto generated ITC statement amounts; the intimation (FORM GST DRC-01C Part A) directs the registrant to either pay the excess with interest via FORM GST DRC-03 or furnish reasons on the common portal within seven days. The registrant must record payment or explanation in Part B of FORM GST DRC-01C. Non-response or unacceptable explanations lead to demand and recovery under the assessment provisions. Guidance also stresses proper return reporting and classification of ITC reversals.