When a married couple files a joint tax return, each spouse is “jointly and severally” liable for the full amount of tax on the couple’s combined income. Therefore, the IRS can pursue either spouse to collect the entire tax — not just the part that’s attributed to one spouse or the other. This includes any tax deficiency that the IRS assesses after an audit, as well as any penalties and interest. But there may be relief. A brief sidebar addresses what to do about future returns.