The world’s tax collectors have been gunning for Silicon Valley. Now they’re trying to figure out how to divide up the spoils.

For years, U.S. tech giants like Alphabet Inc. and Facebook Inc. have shifted around profit so they pay little income tax in many countries where they operate. More than $600 billion in profits, or 40% of multinational profits, were shifted in 2015 to low-tax countries such as Ireland, the Netherlands and Bermuda, according to one estimate.