state by state thing, i bet. i know arizona and florida do it because i've lived both places. apply to state, they pull it from the road tax section, apply it to the aviation tax section (both state and federal), and refund the difference. at least, they say they move it from fund to fund, and i trust the government. if aviators don't file, or if the state doesn't allow us to file, then the aviation fund gets shortchanged when we use autogas in aircraft. not good.