Dear (Mr./Miss/Mrs./Ms.) followed first and last name,
We want to express our appreciation for your participation in the ___________ (course name) that was conducted from ___________ (beginning date of course) to _____________ (ending date of course).
This certification letter is to inform you that you have successfully completed the course, and that you have been certified with ___________ (grade, marks, etc.) If the grade or mark for the course will be sent at a later date, state that fact in this area.
We wish to extend our congratulations, and hope that by attending this course/training you have achieved the knowledge you desire to enhance your future endeavors.
Signature of signing authority
Sign your name by hand above your typed signature. As you can see, a certification letter is very brief and contains only pertinent details. Avoid including irrelevant information, and write in a concise, professional manner.