CHRIS KLINTON
1234, West 67 Street
Carlisle, MA 01741
(123)-456 7890
[Subject: Normally bold, summarizes the intention of the letter] -Optional-
Dear CHRIS KLINTON,
I am very grateful to you for your gesture of taking my kids down to the zoo on Sunday. But, I am afraid that some sudden circumstances have turned up necessitating us to travel on that day disrupting the earlier plan. However, I am very much thankful for your thoughtfulness and hope we can do this again some other day.
Sincerely,
Randolph