Q. I have a question about the use of a hyphen in a compound modifier after a noun if a form of the verb “to be” is used. For example, “He is a well-known man” is hyphenated because the compound modifier comes before the noun. What about “The man is well known”? I’ve looked at various sources and they seem to contradict one another.
A. The placement of a compound modifier after a noun frequently involves the use of a “to be” verb, so yes, the rule applies in that situation. In your example, “well known” is open after the noun. You can find more examples in the hyphenation table at CMOS 7.89.