If they have your permission and you signed off on it, then yeah if you are filing a simple federal form. As for state taxes, you may want to have some who knows your state taxes rules for deductions that are beyond simple deductions because they may not be aware of certain things you can write off in your state and all the taxes you may have to pay. Some places charge city taxes on top of state and federal. But a simple form that you fill at home is usually not an issue.

Yes. When I lived in Colorado, I kept my accountant from Seattle, and she filed for me every year. Come to think of it, she still did my taxes when I moved to Connecticut, until she retired.

Yes.

If you have a state income tax you might prefer to use someone local, but an out of state accountant can still do it. They will have to take the time to look up your state requirements. If you have a local business then also having a local accountant can be useful.

If you just pay federal income tax then that’s the same no matter where you live.

Yes, but when they/you are done filling out the forms, the person whose name is on the forms has to sign them unless you, the person filing the forms, are authorized, legally, to sign instead of the person whose taxes you are filing.

I had both my state and federal returns done by someone in another state some years ago. The only thing is that she had to send my federal returns to a different IRS center than I would have from here. Anything in the future relating to those returns went through the service center where she originally filed.

Yes. I have clients all over the country and internationally. I e-file on behalf of them all.