Workers over 50 who earned above a statutory wage threshold in the prior year can no longer treat their 401(k) catch-up contributions as pre-tax deferrals. Treasury and the IRS finalized regulations under the SECURE 2.0 Act requiring those contributions to go into a Roth account, meaning the money will be taxed upfront rather than at withdrawal. The rule, codified in Section 603 of Public Law 117-328, Division T, carries a sharp penalty for plans that fail to add a Roth option: affected participants could see their maximum allowable catch-up contribution drop to zero.
Why the Roth Catch-Up Rule Changes Retirement Math for Older Workers
The final regulations, published as T.D. 10033 in Internal Revenue Bulletin 2025-40, generally apply to contributions in taxable years beginning after December 31, 2026, per the IRS. That means the 2027 plan year is the first full cycle in which most employers must comply. A separate IRS participant-facing guidance page on catch-up contributions, however, states that “beginning in 2026, if a plan has Roth features and offers catch-up contributions, participants above the prior-year wage threshold must make catch-up contributions on a Roth basis.” The two timelines create a practical question for plan sponsors deciding when to act.
The gap matters because plan administrators need lead time to update payroll systems, amend plan documents, and communicate the change to participants. Plans that already offer a Roth 401(k) option are better positioned. Plans that do not face a binary outcome spelled out in Treasury regulation 1.414(v)-2: if a plan lacks a Roth feature, the maximum catch-up contribution permitted for impacted higher-wage participants can be zero dollars. That is not a technicality. It is a complete loss of the catch-up benefit for those workers.
The hypothesis worth tracking is straightforward. Plans that add Roth features ahead of the compliance deadline should see measurably higher catch-up contribution rates among earners above the threshold than plans that delay or skip the upgrade entirely. No public dataset yet tracks plan-level Roth adoption rates in response to SECURE 2.0, so the evidence will emerge over the next two years as employers file amended plan documents and annual reports.
What Treasury and the IRS Finalized in IR-2025-91
The regulatory package announced in an IRS news release traces directly to Section 603 of the SECURE 2.0 Act, enacted as Division T of the Consolidated Appropriations Act, 2023. Congress created the statutory requirement; Treasury and the IRS wrote the operational rules that tell employers how to implement it.
The core mechanism works like this: a participant age 50 or older whose prior-year wages from the employer exceeded the statutory threshold (indexed annually) must have any elective catch-up contributions treated as designated Roth contributions. In practice, that means the contributions are made with after-tax dollars, grow tax-free, and can be distributed tax-free if Roth holding-period and age requirements are met. Regular deferrals up to the standard 401(k) limit can still be made on a pre-tax or Roth basis, depending on the plan’s options and the participant’s election.
The regulations also clarify how the wage threshold is measured. The test looks to prior-year wages subject to FICA from the sponsoring employer, not household income or outside earnings. Employers must track which participants cross the threshold and adjust payroll withholding accordingly for catch-up amounts. If a participant’s wages fluctuate around the line from year to year, their catch-up contributions may toggle between pre-tax eligibility (if the plan allows it for below-threshold workers) and Roth-only treatment.
For plan sponsors, the most consequential operational rule is the “no Roth, no catch-up” outcome. If a plan offers catch-up contributions but does not provide a designated Roth account, and it has participants whose wages exceed the threshold, the regulations treat the plan as failing the catch-up rules. The cleanest way to avoid that result is to adopt a Roth feature, update payroll coding to identify affected workers, and ensure that catch-up dollars for those workers are directed exclusively to the Roth source.
Employer Timelines and Participant Tradeoffs
The apparent mismatch between the general effective date in T.D. 10033 and the earlier 2026 reference in the IRS participant guidance leaves employers with a strategic choice. Some will move quickly to add or refine Roth features so they can align with the earlier date and avoid mid-year corrections. Others may wait until closer to 2027, relying on the formal effective date while monitoring for additional IRS clarifications.
For older, higher-earning workers, the shift is both a constraint and an opportunity. They lose the flexibility to make pre-tax catch-up contributions once they cross the wage threshold, but they gain forced diversification into a tax-free bucket that may be valuable in retirement. Participants below the threshold retain more choice: if their plan permits it, they can still decide year by year whether catch-up amounts are pre-tax, Roth, or some combination, subject to overall limits.
The next two plan years will reveal how quickly employers adapt. Plans that move early may smooth the transition for workers and preserve catch-up access for all eligible participants. Plans that delay adding Roth features risk leaving a subset of older, higher-paid employees without any catch-up room at all-an outcome that cuts directly against the retirement-saving intent of SECURE 2.0.
