Most states allow spouses seeking a divorce to allege fault in the breakup of the marriage as a basis for the divorce. Alleging the other spouse’s fault—rather than seeking the divorce on no-fault grounds (irreconcilable differences or incompatibility, making the marriage unsustainable)—is generally a basis for requesting the court make an uneven distribution of the marital or community property in favor of the spouse alleging the other’s spouse’s fault.

In states that allow a spouse to seek a divorce on fault grounds, the grounds that may be alleged vary from state to state, but generally include adultery, cruelty, conviction of a felony, family or domestic violence, abandonment, mental illness, and substance abuse (drugs and alcohol). Spouses may also seek a divorce on no-fault grounds in these states.

In no-fault states, a spouse is not allowed to allege fault as grounds for the divorce, and the court is not allowed to consider fault in dividing the marital or community property—but allegations of fault may be considered for other purposes, such as spousal support and child custody. No-fault states include California, Colorado, Florida, Hawaii, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, Oregon, Washington, and Wisconsin. And in some states “incurable insanity” is a no-fault ground for divorce.

The grounds on which a spouse may seek a divorce (fault or no-fault) are usually located in a state’s statutes—often in the family code or domestic relations code.

In Washington (WA), the state operates under a no-fault divorce system. This means that a spouse seeking a divorce in Washington is not required to allege fault on the part of the other spouse. The only ground for divorce in Washington is the irretrievable breakdown of the marriage, which is essentially the same as citing irreconcilable differences or incompatibility. When it comes to the division of marital or community property, Washington courts do not consider fault. The division is based on what the court deems 'just and equitable,' which may not necessarily be equal. However, allegations of fault may still play a role in other aspects of the divorce proceedings, such as spousal support and child custody determinations. It's important to note that while fault is not a factor in the division of property, the behavior of the spouses during the marriage can sometimes indirectly influence the outcome of these other decisions.