Interest adjustment on revised assessments: increased interest triggers a demand notice deemed under payment provisions, reductions give refund. Where a later order under reassessment, rectification or appellate provisions changes the amount on which interest under sub section (1) was payable, interest shall be increased or reduced accordingly; increased interest requires service of a prescribed notice of demand deemed to be a notice under the payment provisions, while reduced interest gives rise to refund of any excess paid. A first-time assessment made under the reopening provision is to be treated as a regular assessment for purposes of the interest, collection and refund rules.