For what it worth from Gray Book 2004-42:
Treas. Reg. §1.401(a)(9)-2, A-2(a) provides that except in the case of a 5%-owner, the “required beginning date” is April 1 of the calendar year following the later of the calendar year in which the employee attains age 70-1/2 or the calendar year in which the employee retires from employment with the employer maintaining the plan. If December 31, 2003 is the employee’s last day at work, and the last day for which he is paid or entitled to payment of wages, is that the date of “retirement”. Or is January 1, 2004, the first day he is not employed, the retirement date? When is the employee’s required beginning date?
RESPONSE
“Retirement” is the last day worked, not the definition of retirement date in the plan. What date is an employee’s last day worked is a facts and circumstances determination. The facts and circumstances are based on the employer’s practice concerning the last day an individual is considered an employee.