Jeff Bezos would have paid $5.7 billion out of his $191.2 billion fortune.
"The ultra-rich and powerful have rigged the rules in their favor so much that the top 0.1% pay a lower effective tax rate than the bottom 99%," Warren said in a statement.
A University of California Berkeley analysis, cited by Warren, estimates that the tax would generate $3 trillion in revenue over 10 years.
The IRS has in recent years audited people earning less than $20,000 a year almost as often as those in the top 1%. In part, that's because it's easier to audit the poor.