To stay afloat, the nonprofit became reliant on money that was supposed to go to payroll taxes, according to its financial statements. The amount National Action Network underpaid the federal government in taxes went from about $900,000 in 2003 to almost $1.9 million by 2006, records show. Mr. Sharpton, making more money from a new radio contract, tried to help by forgoing a salary from 2006 through 2008 and giving the organization a $200,000 no-interest loan.

In 2007 and 2008, the group’s accountant noted in a financial statement that the organization’s “existence has been dependent upon” loans from Mr. Sharpton and “the nonpayment of payroll tax obligations.”

“These circumstances create substantial doubt about the organization’s ability to continue as a going concern,” the accountant wrote.

In 2009, when the group still owed $1.1 million in overdue payroll taxes, Mr. Sharpton began collecting a salary of $250,000 from National Action Network. The recent Treasury report that called that sort of practice abusive also said only 1,200 organizations in the nation owed more than $100,000 in unpaid payroll taxes, which would put Mr. Sharpton’s group among the most delinquent nonprofit organizations in the nation.