Yes — if your spouse (or ex-spouse) understated or failed to report income on a joint return without your knowledge, you may qualify for Innocent Spouse Relief, which releases you from responsibility for that portion of the tax. You must file Form 8857 within 2 years of when the IRS first tries to collect. There are three types: traditional Innocent Spouse Relief (for erroneous items you didn't know about), Separation of Liability (which splits the liability between spouses), and Equitable Relief (a catch-all for situations that don't meet the other criteria). The IRS will notify your spouse that you've applied. This can be a complex process — consider seeking help from a tax professional or a Low Income Taxpayer Clinic.