The name that Republican tax writers gave to a new, multibillion-dollar business levy implies that it targets foreign earnings from "intangible" intellectual property—hitting tech firms and drugmakers like Apple and Pfizer.

But experts agree that the little understood "global intangible low-taxed income" levy, or GILTI, will also apply to earnings that go far beyond patents, royalties, and licensing, and could end up snaring many global firms that earn little such income. Private equity partnerships that aren't publicly traded, including Bain Capital, stand to pay rates three times as high as corporate competitors, tax lawyers say. Law and advertising firms with overseas offices may also be hit—as will many U.S. companies that make "excess" profit from foreign plants, equipment, and inventory.

The name is "Orwellian," James Duncan, a tax partner at the law firm Cleary Gottlieb Steen & Hamilton, said in a Dec. 20 webcast. "Its most significant effect is on income that is neither intangible nor low-taxed."