Certificate for lower or no tax deduction: Assessing Officer may grant relief based on existing and estimated tax liability. Substitution of rule 28AA provides that an Assessing Officer may issue a certificate for deduction of tax at a lower rate or no deduction where existing and estimated tax liability justify such relief; liability is determined by considering estimated tax for the relevant previous year, tax on returned or assessed income for the last three years, existing liabilities under tax laws, advance tax paid, tax deducted at source and tax collected at source up to the application date; the certificate is limited to and issued to the named person responsible for deduction and is valid for the period specified unless earlier cancelled.