Русско-англо-русский юридический словарь

associated company (UK) is a company in which another company has a "significant interest,", that is, a shareholding of 20–50%. An interest of more than 50% is considered a controlling interest (the companies are then parent and subsidiary), while one of less than 20% is considered an investment. In the US the general term is affiliate. (English As a Legal Language by Christine Rossini)

The term "affiliate" means (A) entity that directly or indirectly owns, controls, or holds with power to vote, 20 percent or more of the outstanding voting securities of the debtor, other than an entity that holds such securities [...] (§101(2), U.S. Bankruptcy Code)

An associate is a company in which a group of companies has a substantial stake, but not outright control. This usually means more than 20% but less than 50%. More than 50% would give the group control and make it a subsidiary. (moneyterms.co.uk)