Does anyone know if Treasury Regulations, IRS Code, IRS Procedures, Notices, Rulings etc., references how distributions from a mandatory contributory DB plan should be calculated? (i.e., is it prorated between the ER and EE amounts) Also, If a participant is in pay status (assume J&S 50% calculation) and both the participant and beneficiary die before the total employee contributions are distributed. Is there a special calculation for the contingent beneficiary or participant's estate?

If you are asking how to determine which part is employer and which part is employee, then see regulation 1.411© 1.

If you are asking about the basis recovery rules, I knew those a few years ago but have forever banned them from my memory banks. Check Tax Facts or the Pension Answer Book or the ERISA Outline Book. Or, somebody who has recently taken ASPA's C-3 exam can probably answer that.

...or the regs under IRC section 72.

With respect to the original question where "...both the participant and beneficiary die before the total employee contributions are distributed", it is likely that the plan will already address this.