I looked up state abbreviations. There is no IO.  So no clue what you're talking about.  and this is board for tax professionals.  There are consumer tax boards out there.  Additionally, please consider using the Internet to do a search for your answer since the question wasn't clear.

I was thinking maybe Idaho changed their abbreviation 🤔

Io Jima.  Lots of Marines became heroes there.  

IOwa

IdahO

And there are crypto sites on the TLD (top level domain) = .io

@redial      No