IRS to O.J. Simpson -- Seriously, You Need To Pay Your Taxes!!!

O.J. Simpson may be rotting behind bars, but it doesn't mean he can skate on his taxes ... so says the IRS, who just slapped him with yet ANOTHER tax lien.

According to a federal lien filed in December, O.J. failed to cough up $17,015.99 in taxes for the year 2011. This makes for the THIRD lien filed against him in the last 12 months.

As TMZ first reported, Uncle Sam filed a lien for $179,435.07 for the years 2007-2010 and the State of California says he still owes $318,566.04 for the year 2000. Tax debt total = $515,017.10.

And don't forget ... he still owes MILLIONS to the families of Nicole Brown Simpson and Ronald Goldman for that whole double murder thing.