A more thorough explanation:

The innocent spouse rule is a type of relief offered by the Internal Revenue Service (IRS) to individuals who filed a joint tax return with their current or former spouse and are seeking relief from joint and several liability for tax, interest, and penalties resulting from erroneous items reported by their spouse on the joint return.

Erroneous items can include unreported gross income, incorrect deductions, credits, or property basis claimed by the spouse. The innocent spouse rule provides total or partial relief to the applicant if they had no knowledge or reason to know of the erroneous item.

For example, if a husband and wife file a joint tax return and the husband fails to report income from a side job, the wife may be eligible for relief under the innocent spouse rule if she had no knowledge of the unreported income and did not benefit from it.

To qualify for relief, the applicant must meet three requirements:

1. The joint return has an understatement of tax due to erroneous items reported by the spouse.
2. The applicant did not know and had no reason to know of the understatement of tax at the time of signing the joint return.
3. It would be unfair to hold the applicant liable for the spouse's understatement of tax given the facts and circumstances of their situation.

Additionally, the applicant and their spouse must not have participated in a fraudulent transfer of property. If the applicant meets the requirements, they must file Form 8857 with the IRS within two years of the first attempt to collect the increased tax.

Overall, the innocent spouse rule provides relief to individuals who were unaware of their spouse's erroneous items on a joint tax return and should not be held liable for them.