Interest on delayed tax payment requires prescribed interest from day after due date; higher interest for undue input tax credit. Every person liable to pay tax who fails to remit tax on time must pay interest on the unpaid amount at a Government notified rate (subject to an upper limit), calculated from the day after the tax was due in the prescribed manner. Separately, a taxable person making an undue or excess input tax credit claim or an undue or excess reduction in output tax liability must pay interest on that undue claim or reduction at a higher Government notified rate (subject to a distinct upper limit).