WASHINGTON — Paul Manafort and his former business associate Rick Gates were told to surrender to federal authorities Monday morning, the first charges in a special counsel investigation, according to a person involved in the case.The charges against Mr. Manafort, President Trump’s former campaign chairman, and Mr. Gates were not immediately clear but represent a significant escalation in a special counsel investigation that has cast a shadow over the president’s first year in office.Mr. Gates is a longtime protégé and junior partner of Mr. Manafort. His name appears on documents linked to companies that Mr. Manafort’s firm set up in Cyprus to receive payments from politicians and businesspeople in Eastern Europe, records reviewed by The New York Times show.Mr. Manafort had been under investigation for violations of federal tax law, money laundering and whether he appropriately disclosed his foreign lobbying.Attempts to reach Mr. Gates on Monday were not successful. A spokesman for Mr. Manafort did not immediately respond to a request for comment.Mr. Manafort has expected charges since this summer, when F.B.I. agents raided his home and prosecutors warned him that they planned to indict him. That warning raised speculation that Mr. Manafort might try to cut a deal to avoid prosecution.Mr. Trump’s lawyer, Ty Cobb, said there were no concerns that Mr. Manafort would offer damaging information about the president in exchange for a deal.Some close to Mr. Manafort, including his former business partner Roger J. Stone Jr., have said he had nothing to offer that would help prosecutors build a case against Mr. Trump.“He’s not going to lie,” Mr. Stone said in September.Mr. Manafort, a veteran Republican strategist, joined the Trump campaign in March 2016 to help keep delegates from breaking with Mr. Trump in favor of establishment Republican candidates. Mr. Trump soon promoted him to chairman and chief strategist, a job that gave him control over day-to-day operations of the campaign.But Mr. Trump fired Mr. Manafort just months later, after reports that he received more than $12 million in undisclosed payments from Viktor F. Yanukovych, the former Ukrainian president and a pro-Russia politician. Mr. Manafort spent years as a political consultant for Mr. Yanukovych.American intelligence agencies have concluded that President Vladimir V. Putin of Russia launched a stealth campaign of hacking and propaganda to try to damage Hillary Clinton and help Mr. Trump win the election. The Justice Department appointed Robert S. Mueller III as special counsel in May to lead the investigation into the Russian operations and to determine whether anyone around Mr. Trump was involved.Mr. Trump has denied any such collusion, and no evidence has surfaced publicly to contradict him. At the same time, Mr. Trump and his advisers this year repeatedly denied any contacts with Russians during the campaign, only to have journalists uncover one undisclosed meeting after another.The New York Times revealed in July that Mr. Manafort and others close to Mr. Trump met with Russians last year, on the promise of receiving damaging political information about Mrs. Clinton.