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 come after 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. (However, the civil fraud penalty can be imposed only on spouses who’ve actually committed fraud.) So, if you’re married and file a joint return, what happens if your spouse doesn’t disclose all of his or her income or otherwise doesn’t pay the correct tax owed? You’re generally liable for the full amount, but...