Manny Pacquiao's financial problems are starting to build up. He now has a bill of $18 million dollars ... in addition to his $50 million dollar tax fight in the Philippines ... and this time, it's Uncle Sam that's trying to force Manny to pay up.
TMZ Sports has obtained official documents which show the IRS claims Manny owes the government millions in federal income taxes from 2006 to 2010 ... totaling $18,313,668.79 in debt.
Here's the yearly breakdown:
2006 -- $1,160,324.30
2007 -- $2,035,992.50
2008 -- $2,862,437.11
2009 -- $8,022,915.87
2010 -- $4,231,999.01
Interesting note -- Manny had 3 big fights in 2008, including a match against Oscar De La Hoya in which MP reportedly banked $15-$30 million in guaranteed cash.
In 2009, Manny famously fought Ricky Hatton and Miguel Cotto.
Manny's U.S. tax problems come on the heels of a nasty tax war in his home country, the Philippines ... where the goverment claims he evaded paying $50 million in taxes in 2008 and 2009 stemming from fights that took place in the United States.
Philippines officials have frozen the bank accounts Manny has in the country ... and even placed a lien on one of his most expensive properties, located in Manila.
We reached out to Manny's camp -- so far no word back.