For a participant who has reached the participant’s applicable age, the Treasury’s rule sets the § 401(a)(9)(C) required beginning date as the April 1 that follows “[t]he calendar YEAR in which the employee retires from employment with the employer maintaining the plan.” 26 C.F.R. § 1.401(a)(9)-2(b)(1)(ii) (emphasis added) https://www.ecfr.gov/current/title-26/part-1/section-1.401(a)(9)-2#p-1.401(a)(9)-2(b)(1)(ii).
If, by December 31, neither the employer nor the employee communicated to the other an end of the employment, it might be a good-faith interpretation to presume the employee had not THEN retired from employment. If so, the following April 1 would not be the required beginning date, even if before April 1 (but after the preceding December 31), the employer or the employee decided to end the employment.
A rule interpreting a severance from employment, although for a different tax law condition, suggests that a mere expiration of a nonemployee’s work period might not be a severance “if the eligible employer anticipates a renewal[.]” And that’s so even if whether the worker is reengaged depends on whether the employer needs the worker’s services, whether the employer has money to pay for the services, or both. See 26 C.F.R. § 1.457-6(b)(2)(i) https://www.ecfr.gov/current/title-26/part-1/section-1.457-6#p-1.457-6(b)(2)(i).
This is not advice to anyone.