In a divorce, the court recognizes that a valid relationship no longer exists. An annulment, on the other hand, means the court rules that a marriage never existed, retroactively voiding the marriage.

The law describing annulments is found in 43 Oklahoma Statutes Annotated 3, 126, and 128.

Annulment rests on a presumption of the parties entering the marriage contract in good faith. However, what might be called "buyer's remorse" and absence of intimate relations are not sufficient grounds to annul a marriage. Contrary to popular belief, a judge cannot annul a marriage in Oklahoma simply because the marriage lasted only a few weeks or months. Failure to consummate a marriage sexually is also not grounds, by itself, to annul a marriage.

A marriage can be annulled for any of the reasons that a contract can be overturned. In Oklahoma, an annulment may be granted if a marriage was illegal. Illegal marriages are void and prohibited by law. Living together does not make them valid. Void marriages include incestuous marriages, which are those to a close relative, and bigamous or polygamous marriages, which are those when one or both spouses are already married to another living person.

Voidable marriages are those that are valid but can be declared void under certain circumstances. Grounds for voidable marriages can be waived by cohabitation after the condition is discovered. Voidable marriages include:

If a party continues to cohabit after an incapacity ceases, such cohabitation may be a defense against the request for annulment. Also, for example, if an underage spouse continues living with the other spouse after reaching the age of majority, and then brings an action for annulment later, that continued cohabitation provides the other spouse with a valid defense against annulment.

Getting an annulment in Oklahoma is difficult because the petitioner must demonstrate that the marriage contract itself was not valid. Some jurisdictions consider impotence or insanity grounds for an annulment; however, in Oklahoma the petitioner must prove that the marital contract was void or voidable at the time when it was contracted. In most cases, a no-fault divorce may be easier than an annulment, particularly if the parties agree about the division of property.

For an annulment the petitioner must be a resident of Oklahoma for six months "in good faith" and a resident of the county of filing for more than 30 days.

The clerk of the district court provides the form for the annulment petition, which is completed by the petitioner, and filed. The complaint sets forth the facts of the marriage and the reasons for the annulment and includes:

The form is filed and appropriate fees are paid. The court sets a hearing that both partners attend. At the hearing, the judge decides the case. If granted, an annulment decree will be signed and entered, and the marriage will become void immediately and retroactively. If denied, the parties may appeal or choose a divorce.