When you file a joint income tax return, both you and your spouse are legally responsible for the entire tax liability, known as joint and several liability. This means you are accountable for the tax shown on your return as well as any additional tax the IRS determines is due, even if it stems from your spouse's or former spouse's income, deductions, or credits. You remain liable for these taxes, and the IRS can collect them from you, even if you divorce and your divorce decree states that your former spouse is solely responsible for the tax.
If you believe that only your spouse or former spouse should be held responsible for all or part of the tax, you can request relief from the tax liability, including related penalties and interest, by filing Form 8857. The IRS will review the information you provide on the form and any attachments to determine if you qualify for relief. They will contact you if additional information is needed.
Married individuals who did not file joint returns but lived in community property states may also request relief from liability for tax attributable to an item of community income. Community property states include Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin.