Same-sex couples under the age of 62, who had not previously taken action to convert their Washington state registered domestic partnership to a marriage, are deemed married as of June 30, 2014.  However, for purposes of Washington state law, the legal effective date of the deemed marriage will be the date the couple originally entered into their registered domestic partnership.  Employers and plan sponsors should consult with benefits counsel to properly implement this change of an employee’s marital status for income tax withholding and other employee benefit plan purposes, for example, to determine whether beneficiary designations of someone other than the employee’s former domestic partner, now spouse, remain valid.

A copy of a notice from the Washington Secretary of State’s office discussing this change can be found here

A copy of the Washington state law authorizing same-sex marriages and the conversion of domestic partnerships to marriages can be found here.