Considering the amount of money that the IRS says you owe, you can't afford to make a mistake dealing with this or miss a deadline for responding. The situation could get a lot worse if you don't handle it properly. I suggest that you go immediately to a local tax professional. You don't want someone who just prepares tax returns. You need someone who has experience representing taxpayers in dealing with IRS problems. Whatever you have to pay the tax pro will be well worth it.