Are they oblagated to mail you a check when you quit and you've moved out of state?

Answers:
yes, if you are due one.

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Meaning quitting a job? I think they would, out of courtesy.

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quit what? a job? yeah they are. only if you give them a new address. they don't have to hunt you down.

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This may very by state to state, maybe not. In AZ an employer has 72 hours after termination to get a check in the mail (TO THE LAST KNOWN ADDRESS), not necessarily in the hands of the employee. If they weren't given the new address, there might be a delay as the post office reroutes it. If they FedEx or UPS it to the wrong address then it will go back to them.
They are not at fault if you don't give them a forwarding address. If you don't see it after a week or so I'd call them and get it straightened out. Chances are they're going to want to get you paid and gone because they don't want to waste time on an employee that doesn't work for them anymore...