Business corporations are referred to as kaisha (会社) and are formed under the Companies Law of 2005. There are currently (2015) 4 types and each of them has legal personality:

• 株式会社 (kabushiki-kaisha or kabushiki-gaisha, "K.K.") - lit. "stock company," the most typical form of business corporation.
• 有限会社 (yūgen-kaisha or yūgen-gaisha, "Y.K.") - lit. "limited company," a close corporation form for smaller businesses, abolished in 2006
• 合同会社 (gōdō-kaisha or gōdō-gaisha, "G.K.") - lit. "amalgamated company," a close corporation form similar to the American LLC, introduced in 2006, used instead of abolished "Y.K."
• 合名会社 (gōmei-kaisha or gōmei-gaisha, "GMK") - corporation similar to a general partnership
• 合資会社 (gōshi-kaisha or gōshi-gaisha, "GSK") - corporation similar to a limited partnership

Partnerships are referred to as kumiai (組合). Each of these 4 types has no legal personality though other corporations, which include "kumiai" in their name, have:

• 任意組合 (nin'i kumiai, "NK") - general partnership (Civil Code)
• 匿名組合 (tokumei kumiai, "TK") - anonymous partnership, an investment bilateral contract (Commercial Code, Book 2 Ch.4 Article 535 et seq)
• 投資事業有限責任組合 (tōshi jigyō yūgen sekinin kumiai) - limited partnership for investment (Limited Partnership for Investment Act 1998, Rev.2004)
• 有限責任事業組合 (yūgen sekinin jigyō kumiai) - similar to a Limited Liability Partnership (Limited Liability Partnership Act of 2005)