Taxman, McGregor coming after Mayweather

The IRS says it's still waiting for its cut from Floyd Mayweather Jr. from his nine-figure payday against Manny Pacquiao.

The undefeated boxer nicknamed "Money" owes $22.2 million US in taxes from 2015, according to a notice of a federal tax lien filed by the IRS.

The notice shows the balance unpaid as of March 6. The lien was filed with county officials in Las Vegas in April, and the boxing champ last week filed for a temporary reprieve with the U.S. Tax Court.

Still, the boxer who regularly flaunts his wealth defended himself on Facebook on Monday, saying his "empire is rock solid" and the IRS "just wants to be part of the `Money May' show."

"While everyone is counting my money and assuming the worst, these are the facts... Uncle Sam, received $26,000,000.00 from me in 2015! What else could they possibly want?" he wrote in a post with a picture of a handwritten ledger that showed three amounts totaling $26 million. "I'm sure I would have been notified much sooner if there were any real discrepancies right?"

Mayweather's tax troubles come as prepares for a boxing match against Irish MMA star Conor McGregor in August in Las Vegas. Mayweather, 49-0, will be ending his retirement to face McGregor at T-Mobile Arena.

Both fighters could earn big

Depending on pay-per-view sales, both fighters could earn huge purses, though probably not the $200 million or so Mayweather earned for the fight against Manny Pacquiao.

The men on Tuesday appeared at a news conference in Los Angeles to promote the fight, the first of four this week. There's been plenty of trash talk around the fight, and McGregor didn't miss the opportunity to attack Mayweather.

"The reason he has accepted this fight to come out of retirement is because he has to," McGregor said. "He's in a dire situation. That is not a good situation to be in."

Mayweather told reporters he "already took care" of his taxes.

"I ain't worried about that. I just showed you all a $100 million check I didn't even cash onstage," he said, referring to a check from his fight against Pacquiao. "So we ain't tripping on that."

His tax attorney did not immediately return a request seeking comment.

Appeals process may be buying time

It's unclear whether the IRS has tried to withhold on Mayweather's purse from the fight against McGregor. The agency does not comment on individual cases. Nevada boxing regulators did not immediately return a request for comment.

Generally, the IRS freezes any collection activity as soon as a taxpayer contests a lien. Mayweather petitioned the D.C.-based U.S. Tax Court on July 5 to hear his case in Las Vegas. The petition process comes after a taxpayer and an IRS officer fail to reach an agreement over how a tax debt can be satisfied, said attorney Leighton Koehler, who is with the Las Vegas office of the Dickinson Wright firm and is not associated with the boxer's case.

The appeals process may be buying Mayweather time to collect his millions from the August fight and presumably use the money to pay the IRS. Koehler, who previously worked as an IRS senior revenue agent, said that tax judges only travel to Las Vegas once or twice a year, forcing taxpayers to wait six months to a year before their case is heard.

The lien for 2015 is just the latest in a series of tax liens filed by the IRS against Mayweather over the past decade.

McGregor does not appear to have any tax issues in Ireland or the United States. Ireland's tax website did not include him among a list of delinquent taxpayers for 2015, 2016 and the first quarter of 2017. He did not have any cases in U.S. Tax Court or any liens filed against him in Nevada, Massachusetts or New York, the states where he has fought.