Originally Posted by Abovo

The SDI is also a way for the Franchise Tax Board to track who is working in the state. That's then compared to who paid CA income tax. If you didn't pay CA income tax but you did pay SDI they'll send a letter telling you to pay the tax. Send one back stating that you're a pilot and 98% (depending on fleet, could be 100%) is interstate or international and therefore you're not subject to state income tax. If they want to push it I suppose they might ask for proof but I've never seen it go beyond a letter with that statement.

Proof could be a picture of a United route map, a pile of logbook entries, or a picture of a 747.

When I was nabbed for it I was flying a Brasilia and unfortunately 52% of my flying was intrastate so I had to pay the tax (yes I could have lied and told them it was less than 50%). My home state refunded the income tax to me because double taxation is illegal.