you can usually reduce the taxes you owe by spreading out the back pay for the years that it is for. in other words you can file so that all of the backpay isnt for 2012, it can be applied to 2011, 2010 etc for whatever years it covers.

http://www.irs.gov/publications/p915/ar02.html

http://www.irs.gov/publications/p915...blink100097893