Austin Parker,
1234, West 67 Street,
Carlisle, MA 01741,
(123)-456 7890
[Subject: Normally bold, summarizes the intention of the letter] -Optional-
Dear Austin Parker,
By mistake, I missed the final deadline to register for the business seminar. I really did not know about the date, and wold actually like to attend it. If it is possible, please include me the list. I shall make a payment through check as soon as you accept my proposal on this. I thank you in anticipation.
Sincerely,
Aasia