[DATE, ex. Wednesday, June 11, 1998] 

[NAME, COMPANY AND ADDRESS, ex.
John Smith
XYZ Inc.
1234 First Street
Suite 567
Anycity, Anystate  85245] 

Dear [NAME, ex. John Smith], 

It has come to my attention that your order of [DATE, ex. May 27] for [LIST PRODUCTS, ex. 5 Magnaflux compressors] was delivered late on [DATE, ex. June 27].  Please accept my apologies and let met assure you that our company otherwise has a favorable record of delivering by the date we specify.

I hope the delay did not cause you much inconvenience and we look forward to serving you again.  Feel free to call me at XXX-XXXX if you have any concerns you wish me to address. 

Sincerely,

[YOUR NAME, ex. Jill Jones]