I am an active duty service member currently residing in a U.S. state as a legal resident that filed income taxes last year and state taxes were deducted. While reviewing tax information and working on filing for this year, I had been informed (I had e-filed, both years) that as an active duty service member residing in this state that I do NOT pay state taxes. There have been zero changes to my living situation, marital status, state of residency etc. in the last year.

Who would I contact/how would I go about getting that money back from the state? Should I contact the IRS and take it up with them? I'm unsure of the process and am not having much luck researching the information.

#1;Different states have different rules for taxing military pay. In general, UNLESS the state where you are residing is your home state, you are NOT subject to state tax to the state. Military personnel and their families have special rules for their state tax situation. You will pay taxes to your home state even you are stationed at another state. That is why, many in military claim Washington, Texas, Tennessee and Florida or etc. as their home state because these state have NO state income tax. However, if you earned income from outside job in another state, then, you need to report the income that you earned in the state to the State as a nonresident/ or a resident of the state and can claim the tax that you paid to the state on your home state return.
Note; the family member of the military person MUST pay taxes on income earned within the state borders of the state where the family is stationed. Most states have them report as residents, but some have them report as non-residents. It varies from state to state. However, the family members are NOT normally obligated to report their other "world-wide" income on the state return where they are currently stationed, because the courts recognize that the family members also share the domicile status of the military member himself. You have to file State taxes if your home state has income taxes. Some states exempt military income if you are stationed somewhere outside that state (Illinois, for example). Other states might tax it or a portion of it.You need to contact the Dept of Rev of your home state.

#2;You need to file a non-resident return with the state. Claim zero in state taxable income and receive a refund for the total amount withheld for the state taxes. Then file your home state return as usual.

#3;please contact the Dept of Rev of the state(FTB for CA) for more in on your refund.