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:
- On the left panel, click Workers.
- Click the Employees tab, and click the employee's name.
- Click the pencil icon next to Pay.
- Under What are (employee name) withholdings?, click the pencil icon.
- Update the Home address, then click Done.
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.