Mandatory Roth Catch-Up Contributions in 2026: Who the $150,000 Wage Test Catches.

A 55-year-old engineering director has run the same play for years: max the 401(k) salary deferral, add the age-50 catch-up on top, deduct every dollar. In January 2026 her first paycheck looks different. The regular deferral still goes in pretax, but payroll routes the catch-up to a Roth account, and the deduction for that slice is gone. Nothing is broken. Mandatory Roth catch-up contributions took effect in 2026, and whether the rule applies to you comes down to one number on last year's W-2.

Section 603 of the SECURE 2.0 Act, passed in December 2022, added IRC §414(v)(7). On paper it applied to taxable years beginning after December 31, 2023, but plans and payroll providers were nowhere near ready, so Notice 2023-62 declared 2024 and 2025 an administrative transition period during which pretax catch-ups from high earners would not be treated as violations. That grace ended on December 31, 2025. Treasury published final regulations on September 16, 2025 (T.D. 10033), and they did not extend the transition. The regulations themselves formally apply to contributions in taxable years beginning after December 31, 2026, and for 2026 a plan may operate on a reasonable, good-faith reading of the statute. Do not let that layering fool you: the mandate binds in 2026, and payroll systems started enforcing it in January.

The statute set the threshold at $145,000 of prior-year FICA wages, indexed for inflation. Notice 2025-67 set the figure for 2026 at $150,000, measured against your 2025 wages. The test is specific in three ways that matter. First, it uses Social Security wages as defined in IRC §3121(a), the Box 3 number on your W-2, not Box 1 taxable wages and not Box 5 Medicare wages. Because 401(k) deferrals are still FICA wages, deferring more does not pull you under the line, but pretax health premiums and other cafeteria plan elections do reduce Box 3. Second, exactly $150,000 is not over the line; the statute requires wages that exceed the threshold. Third, only wages from the employer sponsoring the plan count. Someone with two jobs and two 401(k) plans is tested separately at each employer, so a $160,000 job and a $120,000 job produce one plan with a Roth mandate and one without.

One ceiling note: Box 3 was capped at the $176,100 Social Security wage base for 2025, so the wage test tops out there. A $500,000 executive and a $180,000 manager show the same $176,100, and both are over the line. The cap offers no way out.

The exceptions fall out of the wage definition. Partners and sole proprietors have self-employment earnings, not §3121(a) wages, so a solo 401(k) owner who takes no W-2 keeps making pretax catch-ups at any income level. An S corporation owner is different: the W-2 the company issues is FICA wages, so a salary over $150,000 puts the owner squarely under the mandate. New hires escape their first year, because they have no prior-year wages from the employer sponsoring the plan; a job change buys exactly one more pretax catch-up year. And anyone under 50 has no catch-up to worry about in the first place.

The harshest edge cuts the other way. If a plan offers no designated Roth feature, §414(v)(7)(B) bars affected high earners from making any catch-up contribution at all. Most large plans added Roth years ago, but owner-only and small plans that never bothered now have a real reason to amend. The final regulations also bless a deemed Roth election: a plan may automatically treat catch-up dollars from covered participants as Roth once the $24,500 deferral limit is reached, as long as the participant gets an effective chance to opt out of contributing.

The cost is timing, not lost money. The $2,560 in the example is tax prepaid, not tax forfeited, and the $8,000 then grows tax-free with no required minimum distributions from the Roth account during your lifetime. For someone who expects a lower bracket in retirement, prepaying at 32% or 35% genuinely stings. For someone whose retirement balances are large enough that RMDs will keep them in a high bracket anyway, forced Roth dollars are close to what a good plan would have chosen voluntarily, the same logic that drives the mega backdoor Roth.

The realistic levers are narrow but real. If your Box 3 wages hover near $150,000, pretax health, dental, and vision premiums plus HSA and FSA contributions run through a cafeteria plan all reduce Social Security wages, and a few thousand dollars of them can keep next year's catch-up deductible. If you are 60 through 63 in 2026, the enhanced catch-up is $11,250, and the same wage test decides whether it is pretax or Roth, so the stakes are 40 percent higher. If you run your own S corporation, your salary decision now has a side effect on your own catch-up treatment. And if your plan lacks a Roth feature, amend it before the catch-up dollars you expected to make become dollars you are not allowed to contribute.