Question.. If an employee was terminated in Nevada and corporate offices are out of Washington, which laws are in effect for final paycheck?
Was told that final paycheck was "in the mail". Nevada states final paycheck is due immediately, Washington says next scheduled payday. Please help!

Was the employee working in Nevada or Washington?

Employee was working in Nevada

Then Nevada law applies. However, I am not aware of any law prohibiting an employer from putting the check in the mail, as long as it is postmarked the day of the termination.