Rapper Nas, forgot to pay the IRS….he is behind in  $339,000 in taxes which he allegedly kept  for 2010 … and now the U.S. government has obtained a lien on his property.  According to official documents obtained by TMZ, Being a tax scofflaw is nothing new for Nas … according to public records, dude is also on the hook for more than $6 MILLION DOLLARS in back taxes from previous years