Advance tax liability: assessing officer may order payment while taxpayers can submit Form 28A to propose a lower estimate. Every person liable for advance tax must pay prescribed percentages by statutory due dates. The Assessing Officer may issue a written order and notice of demand specifying amounts and installment schedule up to the last day of February when the taxpayer was earlier assessed and is considered liable; such a notice can be issued whether or not installments were paid. The assessee may submit a lower estimate by intimation in Form 28A, which cannot be rejected, or pay a higher self-estimated amount without notifying the Assessing Officer.