It may be impossible to set a minimum threshold for taxable revenue that penalises foreign firms but exempts domestic ones, especially as the latter grow.

ECONOMIST: France and the internet

Similar to the calculation for individuals, the AGI for the taxable year is first reduced by a fixed threshold amount, and then compared to UNII.

FORBES: What the New 3.8% Medicare Surtax Means for You And Your Investments

For each taxable year, the MAGI, after being reduced by a fixed threshold, is compared to NII.

FORBES: What the New 3.8% Medicare Surtax Means for You And Your Investments