Hi there, santabarbara.
Considering that your employee lives and work in CA, their W-4 information should be in CA. However, if they will be moving back to MD and will still work in CA, you can update their address by following these steps:
You can also contact the state of MD to check if you need to pay and file taxes.
Here's also an article for more information about the state reciprocity agreements: Employees Who Work in Another State.
If Maryland (MD) is going to be their new work location, please see article:Add Another Work Location.
Please let me know if you have any additional questions. Thanks.
RE "However, if they will be moving back to MD and will still work in CA"
The OP didn't say the employee was moving.
In any case I don't really understand. How do these steps help the OP change the employee address?
Also, the OP is clear that the employee "work and reside in CA". How then would they be subject to employment taxes in another state? I don't think that's allowed by law. Is there something I don't understand?
I am late to the party, but my understanding is permanent address means this employee is by law a MD not CA resident. So the MD address would have to be correct, however taxes taken out would be only for and submitted to CA.....unless CA and MD have a reciprocity agreement, which I doubt considering the distance.
Also in a case like this, although CA state taxes come out and employee must file a non resident CA tax form for any refund as well as MD state form to pay that no local taxes would come out.
They want to file CA first in hopes of refund before their MD form is due. How do I know this? Family ecperience, employee of DE based company working in PA, OH, NY, no local tax taken out. Family member resident and living in PA, working in OH