Interest is applicable on delayed payment of tax at the rate to be notified (not exceeding 18%) and on undue or excess claim of input tax credit or on undue or excess reduction of output tax liability at the rate to be notified (not exceeding 24%), calculated from the from the day succeeding the day on which such tax was due to be paid Interest is applicable in case of undue or excess claim of input tax credit as well (Section 50).
(ICAI FAQ PUBLICATIONS 06-09-2017 INTEREST ON DELAYED PAYMENT OF TAX: FAQ NO. 34)