The big reason people do an S-Corp is to avoid double taxation (and to be a corporation rather than LLC while not having the complex structures of a C-Corp). Better than being a sole proprietor. Keep in mind that S-Corps can only have a certain number of shares and shareholders (100?) in one class of stock, so a startup or large corporation can't be an S-Corp and take advantage of the tax benefits. Also, here in California, all corporations (S and C and even LLC) owe tax even if the company's net income is zero.