I am working in Germany as a Department of Defense civilian employee. My state of record is Illinois. Should me income be reported as earned while working in Illinois?

[ToddL · Accepted solution]

Unless you take steps to establish legal residence elsewhere (GE or another US state) you are still a legal resident of IL and subject to IL tax law (reporting and paying).

What makes you a resident of a state (or country)? 

Generally, you're a resident of a state (or country) if you intend to either stay there permanently, or return there after a temporary absence. It's where home is – where you come back to after being away on vacation, business trip, overseas or out-of-state employment, or school. Many factors are considered, not the least of which are where you are registered to vote, own homestead property and are licensed to drive.

Residency rules vary from state to state. For example, if you spend more than a certain number of days in some states, you're considered a resident whether it makes sense to you or not. If you have any concerns, check with your State Department of Revenue for specific residency rules, especially as they apply to your particular situation.