A BizWritingTip reader wrote: “A colleague and I are having an argument. If you have to make an abbreviated word plural, do you include an apostrophe? For example, should I write two CEOs or two CEO’s?
BizWritingTip response: If you want to make capital letters and abbreviations ending in a capital letter plural , it is best to just add a lowercase s*
The only time I would use an apostrophe with an abbreviation is if possession was involved.
The CEO’s salary (one CEO)
The MPs’ staff (the staff supporting more than one MP)
*A few reference books do accept the use of an apostrophe before the s (two CEO’s) to form a plural; however, the apostrophe is unnecessary in most instances.