If the IRS attempts to collect the taxes due on a joint return from you and you have since divorced or separated, you may be able to avoid or at least limit your liability by filing Form 8857 to request separate liability relief. If you qualify, you will be liable only for the part of the tax liability (plus interest and any penalties) that is allocable to you. If a tax deficiency is entirely allocable to your former spouse under the rules discussed below, you will not have to pay any part of it. However, you may not avoid liability for any part of a tax deficiency allocable to the other spouse if you had actual knowledge of the income or expense item that gave rise to the tax deficiency that the IRS is trying to collect. See below for details of the knowledge test.
Furthermore, you may not avoid liability to the extent that certain disqualified property transfers were made between you and the other spouse. An election may be completely denied for both spouses if transfers were made as part of a fraudulent scheme.
As with innocent spouse relief (1.7), the separate liability election applies only to tax understatements where the proper tax liability was not shown on the joint return. If the proper liability was shown but not paid, equitable relief (1.9) may be requested.
You may make the separate liability election on Form 8857 if, at the time of filing: