Jimy Ortan,
1234, West 67 Street,
Carlisle, MA 01741,
Cell:-(123)-456 7890.
[Subject: Normally bold, summarizes the intention of the letter] -Optional-
Dear Jimy Ortan,
We are sure you enjoyed the shipment of books sent last week. However, you have not paid the amount of $30 as promised in your agreement. This is a reminder to pay your dues. If you have paid then disregard this notice.
Sincerely,
Wendy