Section 954(b)(4) of the Internal Revenue Code provides a high tax exception specifically for Subpart F income.
According to this section, foreign base company income and insurance income will not be considered as Subpart F income if the taxpayer can establish that such income was subject to an effective rate of income tax imposed by a foreign country that is greater than 90% of the maximum U.S. corporate tax rate.
This provision is designed to exclude from U.S. taxation the income that is already subject to a high level of foreign taxation.