Several kinds of military pay come out of your Oregon adjusted gross income. Pay you earn as a resident stationed outside Oregon is not taxed. Neither is pay earned as a National Guard or Reserve member assigned away from home for 21 days or more, or pay earned by an Oregon National Guard member on state active duty. Whatever taxable military income is left after those subtractions qualifies for a further subtraction of up to $6,000. Military pay or allowances that were never in your federal adjusted gross income are not taxed by Oregon at all.
There is nothing to file separately. Claim the subtractions on your Oregon income tax return. For help, contact the Oregon Department of Revenue.
Your Leave and Earnings Statements and any orders showing where you were stationed or assigned and for how long.