Dear Dr. Smith (or Admissions Committee):
I am writing to notify you of my decision to accept your offer to enroll in the Clinical Psychology program at Graduate University. Thank you for your time and consideration. I look forward to attending your program this Fall and am excited by the opportunities that await.
Sincerely,
Rebecca R. Student
Tailor the letter to your own style and needs. Be sure to sign the letter above your typed name. Congratulations on completing a milestone in your life -- and embarking on a new stage in your education.

