Legal Question in Real Estate Law in Illinois

ANY owner of Illinois real estate as of January 1 of a given year is liable for taxes for that tax year. So if you were an owner on January 1, 2011, for example, you were liable for 2011 taxes payable this year (2012). If there are 2 or more owners, they are considered "jointly and severally liable" meaning any 1 owner is normally responsible for 100% of the taxes; the taxing authorities will not get into issues of apportionment. There are certain exceptions (such as for tax-exempt owners) which most likely do not apply but for any more certainty you can always contact your county assessor and/or treasurer ("taxpayer assistance"), or an attorney who can help you prorate tax obligations properly with the intended grantee and avoid liability.

You have already received one good answer. I would point out that non-payment of the tax bill will impact the property, not so much the owners. You will not be sued for the taxes. The county will "sell" the taxes, meaning another party will pay the taxes and will either be (1) repaid with interest when an owner chooses to redeem the taxes; or (2) be entitled after a couple years to ownership of the property through a tax deed proceeding.

That may not leave you off the hook, however, as you may have some responsibility as relates to your co-owner. You did not provide any background on how you came to be a co-owner, whether there was any agreement between you, why you are wanting out, with whom you co-own, whether that person wants to retain ownership, who is using/living in the property, ... So, it is hard to assess the likely outcomes.