Mistake of Fact for multiemployer plan

Contributions made in error can be returned as a "mistake of fact" (if they qualify) within 12 months of when the mistake was made. But there appears to be an exception for multiemployer plans. Based on what I'm reading in the ERISA Outline Book, "IRC §401(a)(2) provides that a contribution made to a multiemployer plan due to a mistake of fact...may be returned within 6 months after the date that the plan administrator determines that it was made in error". 

If the plan sponsor of a multiemployer plan submits a contribution in error on 2/1/2026 and they determine it was made in error on 2/15/2026, does that mean the deadline to return it is 8/15/2026? Or do they still have the 12 months from when the mistake occurred? 

I assume your question is about an employer that made what it says was a mistaken contribution.

For a multiemployer plan, the plan sponsor is, typically, the plan trust’s joint board of trustees. ERISA § 3(16)(B)(iii), 29 U.S.C. § 1002(16)(B)(iii). Likewise, a multiemployer plan’s administrator is, typically, the joint board of trustees. ERISA § 3(16)(A)(ii), 29 U.S.C. § 1002(16)(A)(ii).

Here’s the statute’s text:

“(ii) if such contribution or payment is made by an employer to a multiemployer plan by a mistake of fact or law (. . .), paragraph (1) [noninurement and exclusive purpose] shall not prohibit the return of such contribution or payment to the employer within 6 months after the plan administrator determines that the contribution was made by such a mistake.”

ERISA § 403(c)(2)(A)(ii), 29 U.S.C. § 1103(c)(2)(A)(ii) (emphasis added), https://www.govinfo.gov/content/pkg/USCODE-2023-title29/html/USCODE-2023-title29-chap18-subchapI-subtitleB-part4-sec1103.htm.

Consider that a multiemployer plan’s joint board of trustees might not determine that what an employer asserts was an ERISA § 403(c)(2)(A)(ii) mistake of fact or law was such a mistake. Further, a joint board might find that, even if there was such a mistake, the employer is for other reasons not entitled to a return of all or some of the mistaken contributions.

Yet, courts have sometimes atextually interpreted or applied the statute. See, for example:

Teamsters Local 639-Employers Health Trust v. Cassidy Trucking, Inc., 646 F.2d 865, 2 Empl. Benefits Cas. (BL) 1217 (4th Cir. Apr. 22, 1981) (analyzing legislative history and common law about what is a mistake of fact for ERISA § 403(c), and what remedy applies) (treating as not obviously wrong the trial court’s finding that the employer’s belief that a contract existed could be a mistake of fact) (ignoring that a multiemployer plan’s administrator determines whether a contribution is mistaken) (ignoring the period for a return of a mistaken contribution to a multiemployer plan) (that the statute permits a return of a contribution made under a mistake of fact does not by itself mean the payer is entitled to restitution).

Ethridge v. Masonry Contractors, Inc., 536 F. Supp. 365, 368 (N.D. Ga. Mar. 25, 1982) (interpreting ERISA § 403(c)(2)(A)(ii) to permit a return of an overpayment without the plan’s administrator’s determination that the contribution was made by mistake of law or fact, or impliedly countermanding, with a de novo rather than deferential review, the administrator’s finding) (interpreting the six-month limit to apply from an employer’s discovery of the mistake, rather than from when the contribution was made or when the plan’s administrator determined the contribution was made under a mistake of law or fact).

This is not advice to anyone.