Grounds for annulment are that the marriage is either void or voidable. A void marriage is one that has no legality whatsoever and is null and void at the time it was made. It can be challenged at any time, even after the death of one of the parties.

A void marriage is one that is also potentially void, but it still remains legal until such time as it is challenged. However, if the spouse has passed away it cannot be challenged later.