"Retired" for determining RMD beginning date

[Guest beppie_stark]

I have an employee who is already over 70.5. He intends to stop working full-time next March but may work part-time or seasonally afterward.

When will he need to take an RMD?

What if he is considered retired and then rehired as a part-time employee?

Do I use the status assigned by our payroll processors or are there regs. that would apply? Would break-in-service rules help determine if a termination of employment has occured?