If you owe the IRS you may have a Federal Tax Lien filed against you. If you do, you can not sell your home unless you pay off your tax liability. You can get a copy of your lien in the county courthouse where you live, but the amount due will be out of date. You have to call the IRS and find out how much is owed currently because interest and penalties have been added to your balance.
You can sell your home if the money you make from the sale of you home is enough to full pay your tax liability. In most cases the only thing to do is to issue checks to the IRS for the taxes and the IRS will automatically release the lien in 30 days from the date the taxes are paid.
In the case that a lien discharge is needed for the title insurance company, you need to apply for a lien discharge with the IRS. Instructions for doing that are here. The really good news is that the IRS is helping to facilitate these discharges in weeks instead of months to help tax payers settle their back taxes.
If you need help with this find a knowledgeable real estate agent and a good tax resolution firm to help with the discharge. The tax firm can research all of your back taxes and help facilitate the discharge by talking with the IRS for you.