How to use possessive form for proper nouns that already have an apostrophe [duplicate]

How would one write a possessive form for a proper noun that already has an apostrophe-s in it? For example, I want to use the possessive form of "McDonald's" maybe in the sentence "The Market Street McDonald's' employees are friendly."

I realize the possessive form may not be entirely necessary there, but in a case where it is, what is correct?

Solution 1:

Technically it could be McDonald's' or McDonald's's because "McDonald's" functions as a singular noun. However, most style guides (and common sense, IMO) suggest you avoid it altogether by rephrasing the sentence:

The Market Street McDonald's has friendly employees.

The employees at Market Street McDonald's are friendly.

McDonald's happens to be a common example used to illustrate it:

Excerpt from The Oxford Dictionary of American Usage and Style

Grammarphobia blog post

Another example on quickanddirtytips.com