So, I have a client that I want to perform some technical services for as an independent contractor. I am a resident of Oregon, and will be performing all work at this client's Oregon location. They told me that I have to fill out a California Form 590 regarding California income tax (the client's HQ is in California).

Since non of the work is being done in California, and I don't reside there, why would I have to send anything to CA for tax purposes? Is my client mistaken? I feel like if I fill this out, they will be obligated to withhold CA income tax from my payments, which makes no sense to me.

Help Appreciated!