Suppose the Irish sub of a U.S. multinational earned $100 pretax, the Irish tax rate is 12.5% and the U.S. tax rate is 21%. Further assume the Irish sub immediately repatriates the remaining after-tax income back to the U.S. parent. Under a territorial tax system how is the income of an Irish subsidiary owned by a U.S. multinational company taxed? What is the total tax on the $100 of income assuming the U.S. firm faces a territorial tax system?

Suppose instead the U.S. firm above faced a worldwide tax system where its income whether earned in the U.S. or overseas was taxed at the US tax rate with a tax credit for foreign taxes paid. What is the total tax on the $100 of income under this system?

What is the purpose of the GILTI introduced in the TCJA of 2017?