Form 16 is a certificate issued by an employer (like PAO/CDA) and it contains the information that you need to prepare and file your income tax return once every year.
Employers must issue it every year on or before 15 June of the next year, immediately after the financial year in which the tax is deducted.
Form 16 is a TDS certificate. The Income Tax Department mandates all employers to deduct TDS on salary and deposit it with the government. The Form 16 certificate contains details about the salary you have earned during the year and the TDS amount deducted.
It has two parts:
Part A with details about the employer and employee name, address, PAN and TAN details, and TDS deductions.
Part B includes details of salary paid, other incomes, deductions allowed, tax payable. In case you lose your Form 16, you can request a duplicate from your employer.