Form 16 is the employer's certificate of tax deducted at source on salary, issued yearly. Part A shows TDS deposited (from TRACES); Part B details salary, exemptions and deductions. Employees use it to file their income-tax return. Issuing correct, timely Form 16s is a hard statutory deadline for payroll.
In India
Must generally be issued by 15 June following the financial year. Errors (wrong exemptions, mismatched TDS) create filing headaches for employees and rework for HR.
In practice
After year-end, an employee receives Form 16 showing ₹18 L gross, ₹1.5 L 80C, ₹17,000/mo HRA exemption and ₹1.1 L TDS. They use it to file their return and reconcile any refund.