Mr. Grinberg, a tax law professor at Georgetown University who worked in the Treasury Department during the Bush and Obama administrations, was initially viewed with skepticism by some progressives, who noted that in 2016 and 2017, he lamented America’s “singularly high corporate tax rate” during congressional hearings and called for the rate to be slashed in favor of a consumption tax.
But in early 2020, Mr. Grinberg wrote in a Foreign Affairs essay that European digital services taxes could open a dangerous front in the Trump administration’s tariff wars and warned that the “decay of the century-long international tax order is likely to accelerate” without a deal. Later that year, Mr. Grinberg alerted Mr. Biden’s campaign advisers on how their international tax proposals meshed with the stalled discussions of a global minimum tax. After the election, he joined Mr. Biden’s transition team.
Ms. Kysar, a professor at the Fordham School of Law and a tax treaty expert, has been a vocal critic of the 2017 Republican tax overhaul. In 2018, she told the Senate Finance Committee that the law’s international tax provisions “fundamentally botched general business taxation.” Ms. Kysar had collaborated on research with David Kamin, deputy director of the White House’s National Economic Council, who helped recruit her to join the transition team and administration.
With the Treasury Department working remotely, Mr. Grinberg and Ms. Kysar spent months juggling Zoom meetings with officials from finance ministries around the world and fielding calls with tax directors from America’s largest companies, which have been anxious about what the agreement will mean for their tax bills.
Working from their basements in Washington and Connecticut, they regularly exchanged emails in real time during negotiations, but they had never met until they traveled to a gathering of finance ministers in Venice in July. At such summits, they would often employ a divide and conquer approach, with Ms. Kysar joining Ms. Yellen in meetings with her counterparts and Mr. Grinberg negotiating separately with Irish tax officials.
The final months of negotiations centered on the United States and Ireland, but with moving parts falling in and out of place from Peru to India, which threatened to back out of the deal shortly ahead the announcement.
Ms. Yellen’s approach with Ireland was to cajole more than to pressure.
“Where once upon a time this tax advantage may have been important to Ireland, Ireland has built a really strong economy with a very well educated labor force,” Ms. Yellen said. “It is an extremely attractive base for American multinationals to choose as their E.U. headquarters.”