Deduction at source rules updated: revised salary withholding rates, perquisite valuation, and documentation requirements affect TDS computation. Deduction of tax at source on salaries for 1979-80 prescribes the rates and increased surcharge for withholding on salary payments from 1 April 1979, sets a non-deduction threshold with marginal relief, and requires valuation of employer-provided perquisites under the Income-tax Rules for estimated salary. It directs inclusion of repayments from compulsory deposit accounts as salary, disallows certain deposits as deductions for withholding, prescribes the standard deduction formula with special limits where conveyance allowance or employer-provided vehicles exist, and specifies documentary and certification requirements for exempt allowances and other deductions affecting tax withheld.