Q. I have an author who is hot under the collar because we replaced all of the ampersands in company names with “and,” per CMOS (14th ed.). The author insists that this is incorrect and that the ampersand is part of the legal name of the company. Can you help me?
A. Your interpretation of the fourteenth edition is correct: CMOS 14 regards ampersands as abbreviations that may be changed to “and” in running text. Exceptions include expressions like “R&D” and names of corporations that are generally abbreviated, such as AT&T, where it would be odd to spell out “and” but not the rest of the abbreviation.
[A couple of decades and a few administrations later:] The seventeenth edition would side with your author (see paragraph 10.24). If a company appears to prefer an ampersand in its name, then write it that way (e.g., Marks & Spencer). If in doubt, you can spell it out. Be consistent.