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. Floyd Mayweather Jr. has had to put his boxing return on ice due to delinquent IRS bills. Mick Akers 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.…