Legally speaking, you might have to. But I still haven’t figured this out yet…
Some details on that one - see this post where I asked the MOEA about “freelancing” in Taiwan:
Besides, there are two kinds of organization in Taiwan: COMPANY and BUSINESS. If you want to be an independent contractor by yourself which not partnership, you can choose a limited company or a sole proprietorship depending on the scale and the business scope.
Yet, starting a sole proprietorship in Taiwan also seems to require almost the same steps as starting a company (including obtaining permission from the investment commission and possibly needing a business address). Which is probably why no sane foreigner would ever do it.