Dear Mrs (Mr)...!
Thank you for your letter of (Date) offering me the post of (...).
I am pleased to accept this post on the terms stated in your letter and confirm that I can commence work on (Date).
I can assure you that I shall do everything I can to make a success of my work.
Yours sincerely,
Источник - "Резюме, характеристики, рекомендации", "Налоговый вестник"