A formal resignation should be very precise, mentioning the post held by the person from which he is resigning. The cause of the resignation should be mentioned in short. And request for the dues referred to in a polite manner.
Here is a sample formal resignation letter:
House no- 50,
Mr. James Lawrence
Genius Electrical Ltd
12th June, 2010
Ref: Resignation from the post of Manager Sales and Marketing
This is to inform you that I am submitting my resignation from the post of Manager Sales and Marketing. Kindly consider this as one months notice from the date mentioned above. As I have received an offer to work with Zenith Group of Companies, I shall be joining their firm in Texas. As this is the place where my wife has her job, it will be convenient for me to be placed there.
I therefore, request you to kindly pay me my dues of the period of one month.