The proposed amendment to 1.417(e)-1 (published 1/17/01) allows for a retroactive annuity starting date. A retroactive annuity starting date requires a make-up payment plus interest to take into account the missed payments.

If the plan does not provide for a retroactive annuity starting date and a missing participant turns up after his or her NRD (and the plan does not provide for lump-sums or actuarial adjustments for delayed retirement) does this participant have to be paid the actuarial equivalent of his or her NRD benefit anyway?

Could the plan now just begin payment of what would have started years ago at NRD?

No. This would effectively cause a forfeiture of a portion of the employee's vested normal retirement benefit. See also Reg. 1.401(a)-14(d).