A NUANS or any other search is not required by the government before applying for trademark registration. Nevertheless, you’d be foolish not to do a search. For one thing, there may already be a registered trademark that’s confusing with yours. Your application will be refused, and you’ll waste time and money. An exact character search will not do, because variations could also be considered confusing. For example, if you searched for koka kola, an exact match search would not turn up coca-cola. Therefore you must also search for similar marks.
The advantage of the NUANS and other similar searches is that they automate the search for sound-alikes. Otherwise, you’d drive yourself crazy thinking up all the possible variations.
You can’t order a NUANS trademark search directly from Industry Canada. You have to go through a NUANS search house.