In October 2017, the U.S. Department of the Treasury and the Internal Revenue Service (IRS) released final regulations prescribing new mortality tables that apply to single-employer defined benefit pension plans for the purpose of calculating the actuarial liabilities for minimum funding requirements, benefit restrictions, and Pension Benefit Guaranty Corporation (PBGC) variable-rate premiums. As with the prior regulations, the new regulations give plan sponsors the option to use either the standard mortality tables developed by the IRS, or to develop plan-specific mortality tables.

The new regulations significantly revised the rules regarding plan-specific substitute mortality tables. Under the prior rules, a plan was required to have fully credible mortality experience in order to use substitute mortality tables. The new rules allow for the use of substitute mortality tables for plans with smaller populations that do not have fully credible mortality experience. As a result, Treasury and the IRS expect that significantly more plan sponsors will request approval to use substitute mortality tables.

Using substitute mortality tables should theoretically improve the fit between expected and actual mortality rates, thereby producing smaller experience gains and losses over time. In addition, for plans employing a workforce that exhibits heavier mortality than the standard tables, using substitute mortality tables could potentially lower both minimum required contributions and PBGC variable-rate premiums.

For these reasons, plan sponsors may want to consider the use of substitute mortality tables. A written request must be submitted by the plan sponsor at least seven months before the first day of the first plan year for which the substitute mortality tables are to apply.

Note that the regulations do not allow plan sponsors to use plan-specific tables for determining minimum lump-sum values; standard IRS tables continue to be used for this purpose.