Interest on default in advance tax payments accrues monthly and may be increased or reduced on reassessment or revision. An assessee who fails to pay interest-tax in advance or pays less than ninety per cent of the assessed interest-tax is liable to pay simple interest at the rate of two per cent per month from the 1st April following the financial year until determination of chargeable interest, calculated on the assessed interest-tax or on the shortfall. Payments made before completion of assessment reduce interest up to the payment date and leave interest on any remaining shortfall; reassessment or appellate orders increase or reduce interest accordingly, with demand notices for increases and refunds for excess.