When a married couple files a joint tax return, both spouses become jointly and severally liable for the income taxes due, including any additional taxes, interest, and penalties determined at a later date. In the event of an underpayment of income tax, the IRS can proceed against either spouse to collect the entire tax deficiency. This places a spouse in a precarious position in situations where the other spouse deliberately omits income or overstates deductions on a jointly filed income tax return, even if the spouse is totally unaware of the other's transgressions. Relief from joint and several liability is available to spouses that signed and filed a joint return for the year in which an income tax deficiency is assessed and who satisfy requirements under one of the following 3 areas: 1. innocent spouse relief under section 6105(b), 2. separate liability relief under section 6015(c), or 3. equitable relief under section 6015(f).
Johnson, Linda M., and Clements, Bruce. "Revised Innocent Spouse Rules Offer Greater Tax Relief." The CPA Journal 72.12 (2002): 60-62.