Is the correct spelling toll-free or toll free?
Confusion arises because there are as many as three possible spellings for compounds (i.e. as one word, two words or two words with a hyphen). Even the experts often don't agree. For writers and editors, hyphenation is definitely a hot topic. In this case, the Gage Canadian Dictionary and the Canadian Oxford Dictionary recommend the spelling toll-free for the adjective and the adverb.
The Canadian Style says that noun-plus-adjective compounds, such as toll-free, are always hyphenated regardless of whether they are used attributively (next to the noun) or predicatively (as an adverb or a predicate adjective). Keeping this rule of thumb in mind should help with similar hyphenation quandaries that you may have.