Interest on delayed tax payment: late payers must self-assess and pay interest from the day after tax becomes due. A person liable for tax who fails to pay within the prescribed period must self-pay interest for the period unpaid at a rate not exceeding eighteen per cent. as notified, calculated from the day after the tax was due in the prescribed manner. Undue or excess input tax credit claims or undue or excess reductions in output tax liability attract interest on the excess at a rate not exceeding twenty-four per cent. as notified.