Nas is great at a lot of things … rapping, feuding … but paying taxes isn’t one of them … and now he’s on the hook for another $339,000 he allegedly kept from Uncle Sam.

According to official documents obtained by TMZ, Nas never forked over $339,005.49 in federal income tax he owed for 2010 … and now the U.S. government has obtained a lien on his property.

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.