“Dark money” is a term used to describe political spending by groups that are not required to disclose their donors. Most often it refers to groups designated by the IRS as 501(c) organizations — businesses, issue advocacy groups, unions, civic and trade organizations (including many nonprofits) which are not allowed to directly contribute to a candidate or campaign, but are allowed to spend money to educate or advocate about issues related to politics or to provide information about where candidates stand on certain issues. (Transparency USA is a 501(c)(3) organization because we provide information and education to the public concerning the money in politics.)