Hi, I think you are referring to a Bonafide certificate, which is essentially a confirmation certificate verifying the employment or address of the employee. There is no prescribed format for such letters. You just need to confirm the employee's employment with your company in simple terms. For example, "This is to certify that Mr./Ms. ___ has been employed with us since..." and so on. Please try to develop a letter on your own to improve your writing skills. We can assist you in correcting it if needed.