Tax deduction at source from salaries: employers must estimate annual salary and deduct tax periodically under section 192. Employers must estimate each employee's salary income for 1997-98, compute tax on that estimate under section 192 at prescribed tiered rates and deduct tax on average at each payment; no deduction is required if estimated salary income does not exceed the exemption threshold. Aggregation rules apply where employees have multiple employers or furnish particulars of other income/TDS (Forms 10E/12C), subject to conditions preventing aggregation if it would reduce tax liability. Deductors must deposit deducted tax timely, issue prescribed certificates and returns (including Form 16 and Form 24), quote TAN, and observe penalties and procedural requirements for failures to deduct, remit or report.