If you are an Ohio resident on active duty and stationed outside Ohio, you can deduct your military pay from your Ohio income tax, and you do not pay Ohio school district income tax on it. The deduction also covers the part of your pay earned while you are on temporary duty outside Ohio for 30 days or more, even if you are normally stationed in Ohio.
There is nothing to apply for in advance. Claim the deduction on your Ohio income tax return for the military pay that is included in your federal adjusted gross income.
Your Leave and Earnings Statements and your orders showing where you were stationed, or your temporary duty orders showing 30 or more days outside Ohio.