(psychiatrist, upon advice of CPA, converted practice from sole proprietorship to a two-member LLC with taxpayer owning 95 percent interest and a "managing" C corporation owning 5 percent; the 95 percent interest was divided between a 10 percent general partner interest and an 85 percent limited partner interest attributable to intangible assets of the taxpayer's practice; second corporation formed to provide services to taxpayer's practice; self-employment tax paid only on general partner interest rather than on entire net income of practice as sole-proprietor; court holds that managing C corp. and service corporation serve no significant business purpose and were mere shells formed only for tax avoidance purposes that are disregarded for tax purposes; LLC becomes single-member LLC and business taxed as sole-proprietorship; taxpayer liable for accuracy-related penalties).