Military Members
Nonresident military personnel
Military personnel temporarily stationed in Washington are presumed to be nonresidents unless they were residents of Washington State when inducted.
Nonresident military personnel on duty in Washington may display any of the following: Washington license plates, plates issued from their official home of record, plates issued from a foreign (out of state) jurisdiction other than your official home of record, until the registration expires. For additional information review the Dept. of Licensing website.
http://www.dol.wa.gov/vehicleregistration/military-inwa.html
WA resident military personnel
If you’re a WA resident temporarily stationed in another state for military duty, you may continue to license your vehicles in Washington State. For additional information review the Dept. of Licensing website.
http://www.dol.wa.gov/vehicleregistration/military-outsidewa.html
Exemptions
Several types of tax exemptions may be available for Nonresidents stationed in Washington and Washington residents stationed outside the state.
http://www.dol.wa.gov/vehicleregistration/militaryexempt.html