This letter apologizes to someone for a misunderstanding.
1234, Main Street
Boston, MA 02123
07 April, 2005
<Recipient Address Goes Here>
I realize that we have had a bit of a misunderstanding regarding <description>. I wanted to tell you that I am sorry for contributing to this error. If I had taken the time to be clearer or to make sure that you understood me correctly, this whole mess could have been avoided. I am sorry if I hurt your feelings or caused you undue stress over this situation. I hope that you will be able to forgive me and that we can learn from this misunderstanding to prevent similar problems in the future.
Please accept my sincerest apologies.
encl: <List of enclosed items goes here>