Here's the Tweet from the DC AG that kicked off a Twitter thread announcing this:
NEW: Today, we’re suing Michael Saylor - a billionaire tech executive who has lived in the District for more than a decade but has never paid any DC income taxes - for tax fraud.

Also, a quote Tweet from a tax attorney (who is also a bitcoiner):
As far as I can tell, @saylor would have had to live in the DC for 183 days or more during the tax year or moved to DC w/ the intent to establish residency. I think he has a place in McLean, VA and Miami, FL. Maybe some others too? This seems like a tall order for DC to prove.