Michael Cohen, US President Donald Trump's former personal attorney, arrives to testify in a closed session before the House Intelligence Committee at the US Capitol in Washington, DC on March 6, 2019.

President Donald Trump's former longtime attorney and fixer Michael Cohen on Thursday filed a lawsuit against the Trump Organization, claiming his former company has failed to pay "fees and costs" related in part to special counsel Robert Mueller's Russia probe.

Cohen argues in New York state Supreme Court that the Trump Organization, where Cohen worked for roughly a decade as an executive vice president and special counsel to Trump, had a "contractual agreement" to compensate Cohen and "to pay attorneys' fees and costs" incurred through his work "with and on behalf of" company officials.

That work involves Mueller's ongoing investigation into Russian election meddling and possible Trump campaign collusion, as well as "multiple congressional hearings," the filing says.

Cohen now says he has "incurred millions of dollars in unreimbursed attorneys' fees and costs" which continue to pile up.

He claims that the Trump Organization owes him $1.9 million in unpaid legal fees and costs. On top of that, Cohen says he is owed an additional $1.9 million that he has been ordered to forfeit "as part of his criminal sentence arising from conduct undertaken" at the behest of the Trump Organization.

Cohen is scheduled to report to federal prison in May for a three-year sentence based on charges lodged by Mueller's team and federal prosecutors in New York. Once a staunch loyalist of Trump's, Cohen broke with his former boss after FBI agents raided Cohen's properties in April 2018.

He pleaded guilty last year to tax evasion and campaign finance violations related to hush money payments made to two women who claim they had affairs with Trump years before he ran for president, as well as lying to Congress about details surrounding an aborted Trump Tower Moscow project.

Cohen testified before multiple congressional committees in public and private hearings at least four times in late February and early March. He accused Trump of committing potentially criminal activity since becoming president.

Attorneys and spokespersons for Cohen did not immediately reply to CNBC's requests for information about the reported lawsuit. Trump Organization lawyer Alan Futerfas did not immediately respond to CNBC's request for comment.

The Wall Street Journal reported in early 2018 that Cohen, weeks before the 2016 presidential election, had arranged a $130,000 payment to porn star Stormy Daniels as part of a deal to keep her from speaking about an alleged tryst with Trump years earlier.

Cohen was also involved in a $150,000 hush deal between Playboy model Karen McDougal and National Enquirer publisher American Media. That deal was also made in the run-up to the 2016 election, and kept her from discussing an alleged affair with Trump. The president has denied the affairs.

Cohen and Trump had both claimed that Trump was unaware of the hush money deal when it was made. But in August 2018, Cohen said while entering a guilty plea in New York court that he worked with an unnamed political candidate to make payments in order to influence the election.

While delivering sworn testimony before the House Oversight and Government Reform Committee on Feb. 27, Cohen alleged that Trump had sent him reimbursement checks related to these deals after becoming president. Cohen provided copies of some of those checks to the committee.

In his opening remarks, Cohen described Trump as a "racist" and a "cheat," and accused him of manipulating his assets for financial gain. Under cross-examination from lawmakers, Cohen testified that federal prosecutors in Manhattan are investigating yet-undisclosed wrongdoing related to Trump.

Cohen was also asked in that hearing who, if anyone, was currently paying his lawyer and spokesman, Lanny Davis.

"At the present moment, no one," Cohen responded.