Uncle Sam filed the lien in Florida earlier this month, claiming Simpson still needs to cough up income taxes from the year 2006.
TMZ broke the story (ies) ... Simpson's knee-deep in tax debt already. He has federal liens against him totaling over $190,000 for the years 2007-2011, and the State of CA issued a tax lien against him for $318,566.04 for the year 2000.
All totaled ... it's about $580,000 of debt.
Hey, we'd say throw his ass in jail ... but he's already there.