29 C.F.R. § 4050.301

(a) In general. This subpart describes PBGC's missing participants program for small professional service defined benefit retirement plans not covered by title IV of ERISA. The missing participants program is a program to hold retirement benefits for missing participants and beneficiaries in terminated retirement plans and to help them find and receive the benefits being held for them. For a plan to which this subpart applies, this subpart describes what the plan must do upon plan termination if it elects to use the missing participants program for missing participants and beneficiaries who are entitled to distributions. This subpart applies to a plan only if it is a single-employer defined benefit plan that—

(b) Individual account plans. This subpart does not apply to an individual account plan under section 3(34) of ERISA, even if it is described in the same plan document as a plan to which this subpart applies. This subpart also does not apply to a plan to the extent that it is treated as an individual account plan under section 3(35)(B) of ERISA. For example, this subpart does not apply to employee contributions (or interest or earnings thereon) held as an individual account. (Subpart B deals with individual account plans.)