Is It More Proper to Use "CC" or "XC" in a Business Letter?
It is acceptable to use either "cc" and "xc" to convey that people in addition to the one to whom the business letter is addressed also received copies. However "cc" is the electronic correspondence default setting, which leads to a general preference for this abbreviation.
The difference between these two abbreviations is that "cc" originally referred to people receiving a "carbon copy" of a letter sent from one person to another, while "xc" was initiated to suggest that recipients were receiving a copy of the letter created with a Xerox machine. Today, it is rare that anyone in business today uses actual carbon paper, but it is also true that duplicates of correspondence are often made with copiers not built by the Xerox company.