Call the labor board and pay the back taxes. Return the key and play it like everything is cool. Smile be polite, dont apologize or admit fault. Do Not get in a confrontation with him! As good as it would feel, just restrain yourself. Return the key before you call the labor board or anyone else. I would do any and everything legally available to you to out him on the curb. Call the BBB as well. Hell call the IRS, ICE, and any other government agency you can think of on him also. Always remember"Never Forgive, Never Forget".