Floyd “Money” Mayweather Jr. is unbeaten in the ring, but his toughest fight yet is with the IRS.

Mayweather, 49, was scheduled to fight Mike Tyson, 59, in an exhibition match this past weekend in the Congo, though the fight never took place and the combatants have been silent about why.

It now seems the Internal Revenue service could be to blame.

Ring Magazine reported that Mayweather was notified by the government agency that it intends to revoke his passport due to a delinquent tax debt of over $7.25 million.

Multiple requests by The Post for comment from Mayweather’s and Tyson’s teams went unanswered.

With Mayweather unlikely to leave the country over potential fears he would be unable to return, the undefeated boxer is now in a mess of trouble outside the ring.

Mayweather announced earlier this year his return to boxing due to financial concerns, including a massive $340 million lawsuit against Showtime.

This possible issue of a delinquent tax bill and being forced to put his boxing career on hold outside the US has put that return on ice for now and potentially at risk going forward.

He is slated for a boxing match with Manny Pacquiao on Sept. 19 at The Sphere in Las Vegas. Initially billed as an official and competitive boxing match, Mayweather later backtracked, calling it an exhibition.

There have been no updates on that fight either, though there is still time to figure out the logistics since it is a stateside bout.

Netflix was announced as the broadcast partner, and Mayweather and Pacquiao are still knee-deep in negotiations.

“I wouldn’t fight an exhibition. It’s either a real fight or nothing,” Pacquiao, 47, said on an April 13 episode of “Inside the Ring.”

With that fight also in limbo, Mayweather’s comeback story has seemingly hit a pretty massive snag.