A court judgment declaring that a marriage was never valid, as distinct from a divorce that ends a valid one - the difference between a void and a voidable marriage, the grounds each state recognises, who may bring the case, and what an annulment does to property, support and children.
An annulment is a judgment that a marriage was legally invalid from the start, so that in law the parties were never married. It is not a religious annulment, which is a separate process within a church and has no civil effect, and it is not a divorce, which dissolves a marriage that was valid. The distinction matters because the grounds are different and narrower: divorce in every state is available without fault, while annulment requires proof of a defect that existed at the time of the ceremony. Statutes divide those defects into two classes. A void marriage is invalid without any court action because the law forbids it outright - bigamy, a marriage between close relatives, and in most states a marriage where one party was below the minimum age with no court or parental approval - though a judgment is usually obtained anyway so that records are clear. A voidable marriage is valid until a court annuls it at the request of the party the statute protects, and the grounds include fraud going to the essentials of the marriage, duress, lack of mental capacity or intoxication at the ceremony, a physical incapacity to consummate that was unknown to the other party, and underage marriage where the minor later disaffirms it.
Who may sue, and for how long, follows from the class. A void marriage may be attacked by either party, by a third party with an interest, or after a party's death; a voidable one only by the party the ground protects, only while both are alive, and only within a period the statute fixes that usually runs from discovery of the defect or from reaching majority. Continuing to live together as spouses after learning of the fraud or after the duress has ended generally ratifies a voidable marriage and bars the claim. The fraud ground is narrower than people expect: misrepresentations about wealth, character or affection do not qualify in most states, while concealment of an intent never to have children, of an existing pregnancy by another person, or of a marriage entered solely for immigration status typically does.
Although the marriage is treated as never having existed, the consequences are not simply erased. Children of an annulled marriage are legitimate in every state by statute, and custody and support are decided exactly as in a divorce. Most states also let the court divide property acquired during the marriage and, in some, award support to a party who married in good faith - the "putative spouse" doctrine, which protects a person who reasonably believed the marriage was valid. Rights that depended on marital status, such as a survivor's benefit or a spousal share of an estate, generally end with the annulment, and a prior spousal-support obligation from an earlier divorce that ended on remarriage does not usually revive. Immigration status obtained through the marriage is affected separately under federal law.
Most people who ask about annulment want a divorce that does not look like one, and a lawyer's first job is usually to say so: if the ground is not there, the case will fail and the time is better spent on the divorce. Annulment is worth pursuing where the marriage was bigamous or prohibited, where a fraud went to the heart of the marriage and was discovered recently, where an earlier support obligation or benefit turned on not remarrying, or where the client married in good faith and needs the putative-spouse protection for property. Because the periods are short and cohabitation after discovery can waive the claim, the advice needs to be sought promptly.
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