(your address)
3rd November 200X
(the name of your boss)
(company name and section work with)
(company’s address)

Dear (the name of your boss),

I regret to inform you that I decided to resign from my present position as (position) with effective from (next day of last date).

Thank you for giving me a chance to learn and to gain the valuable experience in (company name and section work with). I hope my resignation would not cause you much inconvenience.
Thank you for your kind attention and would appreciate if you could let me have a reference letter before I leave.

Yours faithfully,
(your full name)