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 New Hampshire, spouses seeking a divorce have the option to file on either fault or no-fault grounds. No-fault divorce is based on irreconcilable differences that have caused the irremediable breakdown of the marriage. Fault grounds, on the other hand, can include adultery, extreme cruelty, imprisonment for over one year, physical abuse or reasonable apprehension of physical abuse, desertion for at least two years, habitual drunkenness for two years, and joining a religious sect or society that professes the relation of husband and wife void. When fault is alleged and proven, it can influence the court's decisions regarding the division of marital property, alimony, and sometimes child custody. However, many divorces in New Hampshire are filed on no-fault grounds, as it can be simpler and less contentious. The specific statutes governing divorce in New Hampshire can be found in the New Hampshire Revised Statutes Annotated (RSA), particularly in the sections pertaining to domestic relations.