Owner only 401k plan - late deferrals

[Jakyasar]

Owner only 401k plan.

Owner deducted 23k for 2025 on the w-2 but deposited just now.

What kind of correction is needed, if any?

If need to adjust, I am assuming DoL calculator cannot be used, correct?

What other means can be used?

Let's say the correction is $100, is this a deductible expense? If yes, would be for 2026, correct?

Thank you

[Peter Gulia]

Has the business organization yet filed its 2025 income tax returns? Has the individual yet filed her 2025 income tax returns? Or, is either planning toward a September 15 or October 15 due date?

What does the written plan provide about when an elective-deferral contribution is due?

Further, consider that, under the 1978 Reorganization Plan, the Labor department’s interpretation about when a participant contribution becomes a plan’s asset is relevant also for Internal Revenue Code § 4975 about tax-law prohibited transactions. 29 C.F.R. § 2510.3-102(a)(1) https://www.ecfr.gov/current/title-29/part-2510/section-2510.3-102#p-2510.3-102(a)(1).

If there is a contract breach, fiduciary breach, or prohibited transaction to correct, a relevant State’s law might allow a reasonable measure of restoration. Or, the Internal Revenue Service might consider a use of EBSA’s calculator reasonable.

This is not advice to anyone.

[Jakyasar]

9/15 is the deadline.

It is Roth deferral

Thank you for your input