Many military may be overpaying their state taxes, according to analysis done by The Tax Institute at H&R Block.

The institute says that understanding eligibility for the Military Spouse Residency Relief Act can help service members pay only what they owe.

Said Kathy Pickering, executive director of the Institute, "Misinterpretation of the law has likely resulted in many service members and their spouses paying state taxes they didn't owe."

Service members often retain residency status in their home states, despite frequent moves during active duty. The act, which became effective for tax year 2009, allows spouses to also retain residency status in their home state if they move with their military spouse. Under these rules, the spouse's pay earned where they are stationed is not taxed there, but instead in the home state.