Acceptance letter is written by candidate to formally accept the job offer and confirm the details of the employment. Normally, job offer are accepted over the phone, however it is a good idea to accept the same formally so that all correspondence is formal and professional. It should be directed to the person who have offered you a job. It should be price and include the followings
a) Thank you note to the employer for the job offer
b) Written acceptance
c) Date of joining (start date)