29 C.F.R. § 4043.23 — Active participant reduction.

(a) Reportable event. A reportable event occurs for a plan:

(1) Single-cause event.

(i) On each date in a plan year when, as a result of a new single cause, the ratio of the aggregate number of individuals who ceased to be active participants because of that single-cause, to the number of active participants at the beginning of such plan year, exceeds 20 percent.

(ii) Examples of single-cause events include a reorganization or restructuring, the discontinuance of an operation or business, a natural disaster, a mass layoff, or an early retirement incentive program.

(2) Attrition event. At the end of a plan year if the sum of the number of active participants covered by the plan at the end of such plan year, plus the number of individuals who ceased to be active participants during the same plan year that are reported to PBGC under paragraph (a)(1) of this section, is less than 80 percent of the number of active participants at the beginning of such plan year.

(b) Determination rules

(1) Determination dates. The number of active participants at the beginning of a plan year may be determined by using the number of active participants at the end of the previous plan year, and the number of active participants at the end of a plan year may be determined by using the number of active participants at the beginning of the next plan year.

(2) Active participant. “Active participant” for purposes of this section means a participant who—

(i) Is receiving compensation from any member of the plan's controlled group for work performed for any member of the plan's controlled group;

(ii) Is on paid or unpaid leave granted for a reason other than a layoff;

(iii) Is laid off from work for a period of time that has lasted less than 30 days; or

(iv) Is absent from work due to a recurring reduction in employment that occurs at least annually.

(3) Employment relationship. For purposes of determining whether a participant is an active participant, a participant does not cease to be active if the participant leaves employment with one member of a plan's controlled group to become employed by another controlled group member.

(c) Reductions due to cessations and withdrawals. For purposes of paragraph (a) of this section, a reduction in the number of active participants is to be disregarded to the extent that it—

(1) Is attributable to an event described in sections 4062(e) or 4063(a) of ERISA, and

(2) Is timely reported to PBGC under section 4062(e) and/or section 4063(a) of ERISA before the due date of the notice required by paragraph (a) of this section.

(d) Waivers

(1) Small plan. Notice under this section is waived if the plan had 100 or fewer participants for whom flat-rate premiums were payable for the plan year preceding the event year.

(2) Low-default-risk. Notice under this section is waived if each contributing sponsor of the plan and the highest level U.S. parent of each contributing sponsor are low-default-risk on the date of the event.

(3) Well-funded plan. Notice under this section is waived if the plan is in the well-funded plan safe harbor for the event year.

(4) Public company. Notice under this section is waived if any contributing sponsor of the plan before the transaction, or the parent company within a parent-subsidiary controlled group of any such contributing sponsor, is a public company and timely files a SEC Form 8-K disclosing the event under an item of the Form 8-K other than under Item 2.02 (Results of Operations and Financial Condition) or in financial statements under Item 9.01 (Financial Statements and Exhibits).

(5) Statutory events. Notice is waived for an active participant reduction event described in section 4043(c)(3) of ERISA except to the extent required under this section.

(e) Extension—attrition event. For an event described in paragraph (a)(2) of this section, the notice date is extended until the premium due date for the plan year following the event year.

(f) Examples

(1) Determining whether a single-cause event occurred (Example 1). A calendar-year plan had 1,000 active participants at the beginning of the current plan year. As the result of a business unit being shut down, 160 participants are permanently laid off on July 30. Before July 30, and as part of the course of regular business operations, some active participants terminated employment, some retired and some new hires became covered by the plan. Because reductions due to attrition are disregarded for purposes of determining whether a single-cause event has occurred, it is not necessary for the sponsor to tabulate an exact active participant count as of July 30. Rather, the relevant percentage for determining whether a single-cause event occurred is determined by dividing the number of active participants laid-off as a result of the business unit shut down to the beginning of year active participant count. Because that ratio is less than 20 percent (i.e., 160/1,000 = .16, or 16 percent), a single-cause event under paragraph (a)(1) of this section did not occur on July 30. However, if, as a result of the business unit shutdown, additional layoffs occur later in the same year, a single-cause event may subsequently be triggered (See Example 3 in paragraph (f)(3) of this section).

(2) Determining whether an attrition event occurred in year when a single-cause event occurred (Example 2). (i) Assume the same facts as in Example 1 in paragraph (f)(1) of this section except that the number of active participants laid off on July 30 was 230 and thus, a single-cause event occurred. Further, assume that the event was timely reported to PBGC (i.e., on or before August 30). Lastly, assume the active participant count as of year-end is 600.

(ii) To prevent duplicative reporting (i.e., to ensure that the participants who triggered a single-cause reporting requirement do not also trigger an attrition event), the 230 participants who triggered that single-cause reporting requirement are not taken into account for purposes of determining whether an attrition event occurred. This is accomplished by increasing the year-end count by 230. Therefore, the applicable percentage for the attrition determination is 83 percent (i.e., (600 + 230)/1,000 = .83). Because 83 percent is greater than 80 percent, an attrition event has not occurred.

(3) Single-cause event spread out over multiple dates (Example 3).

(i) Assume the same facts as in Example 1 in paragraph (f)(1) of this section except that the layoffs resulting from the business unit shut down are spread out over several months. Table 1 to paragraph (f)(3) summarizes the applicable calculations:

Table 1 to Paragraph (f)(3)
Single-cause event spread out over multiple dates
Date	Number laid-off	Aggregate reduction	Applicable percentage
February 1	50	50	50/1,000 = 5 percent.
May 15	50	100	100/1,000 = 10 percent.
September 1	110	210	210/1,000 = 21 percent.
November 1	40	250	250/1,000 = 25 percent.

(ii) A single-cause event occurs on September 1 because that is the first time the applicable percentage exceeds 20 percent. This event must be reported by October 1. The November 1 layoff does not trigger a subsequent single-cause event because the layoff is part of the same single-cause event already timely reported to PBGC. However, they will be considered in the determination of whether an attrition event occurs at year-end as explained in paragraph (f)(3)(iii) of this section.

(iii) As illustrated in Example 2 in paragraph (f)(2) of this section, for purposes of determining whether an attrition event has occurred, the year-end count is increased by the number of participants that triggered a single-cause event. In this case, that number is 210. The fact that an additional 40 active participants were laid off as a result of the business unit shut down after the single-cause event occurred does not affect the calculation because it was not already reported to PBGC. For example, if the year-end active participant count is 560, the number that gets compared to the beginning-of-year active participant count is 770 (i.e., 560 + 210 = 770). Because 770 is less than 80 percent of 1,000, an attrition event has occurred and must be reported.

(4) Multiple single-cause events in same plan year (Example 4). Assume the same facts as in Example 1 in paragraph (f)(1) of this section except that the July 30 shutdown of the business unit resulted in 205 layoffs on that date. A single-cause event occurred and is timely reported. Later in the same plan year, the company announces an early retirement incentive program and 210 employees participate in the program with the last employees participating in the program retiring on November 15 of the plan year. A new single-cause event has occurred as of November 15 resulting in a reporting obligation of the active participant reduction due to the retirement incentive program (210/1000 = 21 percent).