Q. Are there compounds that are always hyphenated, such as “up-to-date” or “step-by-step,” or are these only hyphenated when modifying another word, as in “up-to-date rules” or “step-by-step procedures”? My company is writing “We’ll walk you through it step by step,” and I thought that it should be “We’ll walk you through it step-by-step.”
A. We prefer to keep such phrases open when they are used adjectivally and appear after the noun they modify, even if they are listed in Merriam-Webster with hyphens:
step-by-step recovery (where “step-by-step” is a phrasal adjective preceding the noun it modifies)
but
feelings that were out of date (because “out of date” follows the noun it modifies)
But when used adverbially, compounds listed as hyphenated adverbs in Merriam-Webster retain their hyphens:
walking across the continent step-by-step (see M-W’s entry for “step-by-step”)
See CMOS 7.96, section 2, under “phrases, adjectival” and “phrases, adverbial.”