The OECD is trying to get nearly 140 countries to agree to an overhaul of global tax by mid-2021.
If that effort fails, a growing number of countries are preparing to launch unilateral measures aimed at tech giants like Facebook Inc. and Amazon.com Inc.
The Organization for Economic Cooperation and Development is leading an effort to address concerns that some multinationals—especially U.S. tech giants—aren’t paying enough taxes in countries where they have users or consumers. The OECD’s two-pillar plan would reallocate profits and set a minimum global tax rate.
Efforts to push unilateral measures may have been aided by the...