A salary certificate is a key document issued by an employer authenticating the salary on which a person is employed in the organization, and its uses can vary.Advertisement. A salary certificate is a detailed and transparent document forming the basis for employee taxation.It gives complete information of the employee, designation, experience, promotions, salaries, etc.ne must note a common misconception with regards to a salary certificate and a pay slip or a salary slip. While a salary certificate is issued for the period employed in a financial year, the latter is issued with respect to a specific month only.