Beginning in August 2000, the Internal Revenue Service was required to obtain detailed registration and financial activity reports from groups structured under Section 527 of the tax code regulating not-for-profit political organizations. Since then, more than 20,000 groups registered as 527 committees. The vast majority of those were not actually 527 committees because they were already filing with state or federal election authorities. Center researchers narrowed this field in search of money raised and spent outside of federal and state campaign finance regulation.
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