The 25 richest Americans paid little to no federal income taxes, according to a report released Tuesday by the nonprofit news organization ProPublica, a claim that has reignited debate about the tax code and sparked an investigation by the IRS into the leak of private tax documents.

NBC News has not independently verified the documents, and ProPublica declined to disclose how it had gained access to what it called a “vast trove of Internal Revenue Service data on the tax returns of thousands of the nation’s wealthiest people, covering more than 15 years.”

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