Like a divorce, annulment ends a marriage. But unlike no-fault divorce, which can be granted for any reason at all simply upon request, annulment has fairly narrow requirements that control eligibility. Whereas divorce terminates a marriage but recognizes its previous existence, annulment treats the spouses as if they were never married at all.
To qualify for an annulment, the law generally requires some flaw in the marriage (called an "impediment") that justifies rendering it invalid. Each state has its own annulment laws, but these requirements fall into three basic categories. Broadly, these are fraud, incapacity and misunderstanding, but some situations can include more than one of these elements.
If one party enters into a marriage due to the force, threat, concealment or misrepresentation of the other, the marriage can be annulled on the grounds of fraudulent inducement. For example, if a wife knows she is unable to have children but fails to inform her fiancé, he can claim the marriage was entered into on the basis of fraud. The concealment of a sexually transmitted disease is also grounds for an annulment on fraudulent inducement.
A marriage can be annulled if one or both of the parties should not technically have been able to enter the marriage. This would occur if either spouse was under 18 at the time of marriage or still in a previous marriage. In most states, a marriage would also be invalid if the parties were close relatives or mentally incapacitated, whether temporarily from intoxication or more permanently from illness. Failure to consummate the marriage through sexual intercourse is also grounds to support an annulment.
For purposes of obtaining an annulment, misunderstanding does not refer to leaving up the toilet seat or forgetting to sort the mail. Only if there is a serious, deal-breaking disagreement that has risen between the parties can a marriage be annulled because of disagreement. An example of a deal breaker would be an important issue that had not been addressed prior to the marriage, such as whether to have children or how to treat certain separate property, and the two cannot come to an agreement subsequent to the marriage.
The duration of the marriage is usually not an issue when determining whether the requirements for an annulment have been satisfied. Most annulments happen within a relatively short period after the marriage simply because the relevant issues tend to surface fairly quickly. If an annulment is based on fraud, the spouse looking to end the marriage should stop cohabiting with the other spouse immediately or risk losing their grounds for annulment. Once a couple has had a child, it's much more difficult to get an annulment for any reason.