CA Payroll vs HI Payroll

Hello.

Client moved to CA a while back and has set up a new s corp for which he needs owner/employee payroll (a service in which I will provide).

In Hawaii, the basics to this are:

1) A WH account
2) A SUTA (UI) account

(employee/owners in HI can be exempt from SUTA, but we pay it anyway due to the way FUTA works and it becomes easier to get benefits if needed)

And that's really all there is to it in Hawaii. WC and TDI are optional for employee owners.

Are there any hidden tricks or traps awaiting me for CA payroll? Does he require CA SDI or something?

He'll need to register with EDD and get a state EIN to report wages and pay SDI and UI. I think you can opt out of SDI as a sole owner, but I've never seen anyone do that. It's only like 1% of wages anyway for SDI so it's not a bad idea to keep it just in case.

Owners can opt out of WC for themselves.

You can opt out of SDI. The wage limit has been removed, so from what I've been hearing from other practitioners, high earners who can are opting out.