(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)