In the United States the term is annulment. Outside this country the term used is nullity.

Both are ways to effectively “erase” a marriage, so – in the eyes of the law – it never existed. Certain circumstances can arise that can render a marriage invalid, or never legal in the first place. 

Basically, there are two types of invalid marriages: those that are void and those that are voidable. Void marriages are those that cannot legally exist and therefore are deemed to never have been valid. Void marriages are generally limited to unions where one party is already legally married to someone else, known as bigamy and those between underage parties, constituting a lack of consent or between close blood relatives, known as incest. In these cases, an annulment (or nullity) would be granted and the marriage would be legally stricken

Voidable marriages are technically invalid but aren’t immediately dissolved and continues as a valid union until an annulment or nullity is sought. This type of marriage doesn’t violate any moral principle (like bigamy or incest), and can become a legal union if circumstances change. An example is where the official presiding over the marriage wasn’t certified, or where the parties were originally underage but have reached the age of consent, and their marriage was never contested. Courts would normally try to honor the marriage if at all possible, if they felt both parties have continued to live as if the union were valid from the start.

In marriages based on deception, many states allow for the deceived spouse to seek a divorce instead and treat the marriage as if it were a valid union. This is known as the putative spouse doctrine and provides certain rights and protections for spouses who are led to believe they’ve entered into a valid marriage through their partner’s deception.

Either one or both of the parties can petition the court to annul the marriage. Unlike a divorce, an annulment or nullity does not provide for alimony and spousal support or division of property. Instead, both parties will part as if the marriage had never taken place, leaving no future obligations between the spouses, unless the couple had children. In this case, child support, child custody and visitation arrangements would be addressed.

To successfully seek an annulment, a request with the court must be filed within a certain amount of time, which depends on several factors, such as where you live, the reason the annulment is being sought, and when a spouse  first discovered the condition or conditions that renders the marriage invalid.

For example, if a couple is seeking an annulment on the basis that one of the spouses defrauded the other, the court would want to know when the fraud was first discovered. If the spouse being deceived discovered the fraud but then continued in the marriage for a considerable time after, the court would be less likely to grant an annulment and the couple would have to seek a traditional divorce instead.