Mary J. Blige -- Money Problems Worsen ... $3.4 MILLION Tax Lien

Mary J. Blige's financial woes have QUADRUPLED -- on top of the $900k she allegedly owes the Garden State, TMZ has learned MJB has been slapped with a $3.4 MILLION bill from Uncle Sam.

The IRS filed a federal tax lien against the Grammy winner, claiming she failed to pay all her income taxes for the years 2009 ($574,907.30), 2010 ($2,203,743.53) and 2011 ($647,604.60).

Tax bill grand total: $3,426,255.43. Translation: A LOT OF FREAKING MONEY.

Of course, the IRS needs to get in line ... the State of NJ says MJB still owes $901,769.65 in back taxes. Blige is being sued for allegedly defaulting on a $2.2 million bank loan and her charity is facing a lawsuit that claims it took out a $250k loan and never paid it back.

Blige's rep tells us, "Mary has been and is continuing to work with her new team to resolve all these issues as quickly as possible."