Tax deduction at source on interest requires prescribed rates, applicable exemptions, certificates, and rounding rules for payers. Deduct income tax and surcharge at prescribed rates from interest on Government securities from April 1, 1973, distinguishing residents and non residents and domestic and non domestic companies; accept operative exemption or abatement certificates and apply certificate specified rates; do not deduct where exemptions apply for specified Bonds, National Defence Loans, designated National Savings Certificates, small holding resident individuals who declare low income and nominal holdings, and exempt Central corporations; round tax fractions to nearest rupee and consult Income tax Officer in doubt.