This seems to be a very common question. First, WA does not have an annulment statute. You can Petition the court to have a marriage declared invalid based upon statutory criteria as set forth below:
RCW 26.09.040 states that a Petition to have a marriage declared invalid may be sustained if:
i) The marriage should not have been contracted because of age of one or both of the parties, lack of required parental or court approval, a prior undissolved marriage of one or both of the parties, reasons of consanguinity, or because a party lacked capacity to consent to the marriage, either because of mental incapacity or because of the influence of alcohol or other incapacitating substances, or because a party was induced to enter into the marriage by force or duress, or by fraud involving the essentials of marriage, and that the parties have not ratified their marriage by voluntarily cohabiting after attaining the age of consent, or after attaining capacity to consent, or after cessation of the force or duress or discovery of the fraud, shall declare the marriage invalid as of the date it was purportedly contracted;
"Annulment" is an act granted by a religious organization to deem a ceremonial marriage to have not happened. "Nullity of marriage" is a legal action to void a marriage. This is not a common way of ending a marriage, which is normally ended by divorce. Marriage can be legally ended by nullity if there was a ceremonial marriage, but the marriage was not legally valid, for example if:
(1) the two spouses are related; (2) either or both spouses was still married to someone else; (3) if one spouse was under age, was legally insane, or married under duress; or (4) if marriage was induced by fraud.
Dissolution of marriage (commonly known as a divorce) requires only that one of the spouses assert that there are "irreconcilable differences." There is no requirement that the other spouse consent to the divorce.
Annulment of marriage
Under certain conditions, a marriage may be annulled. An annulment retroactively makes it as if the marriage never existed.