403(b) After-Tax Contributions: The $72,000 Limit and Roth Conversion

For 2026, after-tax contributions to a 403(b) are limited by what’s left under the $72,000 total additions cap once your elective deferrals and employer contributions are counted against it.¹ If you defer the full $24,500 and your employer adds nothing, you have $47,500 of after-tax room. If your employer contributes $8,000, that room drops to $39,500. The exact figure is personal to your paycheck and your plan, and it depends first on whether your plan even allows after-tax contributions in the first place.

The $72,000 Ceiling and How to Calculate Your Room

Section 415(c) of the Internal Revenue Code caps all “annual additions” to a defined contribution plan.² Annual additions include three buckets: your elective deferrals (pre-tax and Roth), your after-tax contributions, and any employer money such as matches or nonelective contributions. For 2026, that combined ceiling is $72,000.¹

The calculation is straightforward. Take $72,000, subtract your projected elective deferrals, subtract expected employer contributions, and what remains is your after-tax capacity. Elective deferrals themselves are separately capped at $24,500 for 2026 across all your 403(b), 401(k), and SIMPLE plans combined.³ After-tax contributions bypass that $24,500 limit, which is precisely why they exist as a strategy.

There’s also a compensation ceiling. Annual additions can’t exceed 100 percent of your pay for the year.⁴ If you earn $60,000, your combined additions cap at $60,000, regardless of the statutory $72,000.

Check That Your Plan Actually Allows After-Tax Contributions

None of this math matters if your plan doesn’t offer the feature. A 403(b) must have a written plan document, and that document has to specifically authorize after-tax (non-Roth) employee contributions.⁵ Many sponsors skip this option because of administrative burden or nondiscrimination testing headaches. Call your plan administrator and confirm the option exists before you plan around it. If it doesn’t, your ceiling is effectively your elective deferrals plus whatever your employer contributes.

How Employer Contributions Reduce Your Room

Every dollar your employer deposits counts against the same $72,000 cap.¹ Match dollars, nonelective contributions, discretionary employer money: all of it. A generous employer contribution is a good thing, but it directly compresses the space available for after-tax dollars.

Timing complicates the picture. Employer contributions often arrive on a different schedule than your paycheck deferrals, and true-up matches paid at year-end can catch participants off guard. Ask your administrator for a mid-year statement showing total annual additions from every source, and reconfirm before the final payroll of December. If annual additions cross $72,000, the plan must run a correction that can distribute the excess plus earnings back to you.

Catch-Up Contributions Change the Math

Two catch-up provisions can push your total contributions higher, and they interact with the $72,000 cap in different ways.

Age-Based Catch-Ups

Participants who are 50 or older can defer an additional $8,000 in 2026 on top of the $24,500 standard limit.¹ Under a SECURE 2.0 change, participants aged 60, 61, 62, or 63 get a higher catch-up of $11,250.⁶

Here’s the key detail. Age-based catch-up contributions under Section 414(v) are excluded from the 415(c) annual additions limit.⁷ A 52-year-old who defers $24,500 plus an $8,000 catch-up has used only $24,500 of the $72,000 cap. The catch-up sits on top, so it does not reduce after-tax room.

The 15-Year Service Catch-Up

A provision unique to 403(b) plans lets employees with at least 15 years of service at the same qualifying employer increase their elective deferral limit by up to $3,000 per year, with a $15,000 lifetime cap.³ Qualifying employers include public school systems, hospitals, home health agencies, churches, and certain related organizations.⁸

This catch-up is different. It raises the Section 402(g) deferral limit rather than sitting outside the 415(c) cap, so it likely does count toward your $72,000 and reduces after-tax space accordingly. If you qualify for both catch-ups, excess deferrals are applied to the 15-year catch-up first before the age-based catch-up.³

Converting After-Tax Dollars to Roth

The reason most people bother with after-tax contributions is the conversion. Left alone, after-tax money sits awkwardly: contributions were already taxed, but their earnings grow tax-deferred and get taxed again on withdrawal. Moving the money into a Roth account puts both the contributions and future growth into a tax-free bucket. This is what people mean by the “mega backdoor Roth.”

The plan has to cooperate. It needs to allow after-tax contributions and either in-plan Roth conversions or in-service distributions that can be rolled to a Roth IRA. If both boxes are checked, IRS Notice 2014-54 lets you send the after-tax contributions to a Roth account and direct any pretax earnings on those contributions to a traditional IRA, so only the earnings remain tax-deferred rather than triggering current income tax.⁹ Converting frequently keeps the taxable earnings portion small.

Watch the pro-rata rule on partial distributions. Ordinarily a partial withdrawal pulls proportionally from taxable and nontaxable amounts, so you can’t cherry-pick after-tax dollars.¹⁰ The split-rollover method under Notice 2014-54 is the clean way around this.

The Plan-Specific Limit Higher Earners Should Know About

After-tax contributions in a 403(b) are subject to the Actual Contribution Percentage test, which compares contribution rates of highly compensated employees against everyone else.¹¹ For 2026, you’re generally an HCE if you earned more than $160,000 in the prior year.¹

If the plan fails, the employer must correct the imbalance, often by refunding excess after-tax contributions to HCEs and treating those refunds as taxable income.¹¹ Even with plenty of room under $72,000, the ACP test can create a lower, plan-specific ceiling on what you’re actually allowed to contribute.

One important carve-out. Governmental 403(b) plans, including those at public schools and universities, and church plans at qualifying religious organizations, are exempt from ACP testing. If you work for a public school district or a qualifying church, this test is unlikely to limit you.

What Happens if You Go Over

Exceeding the 415(c) cap isn’t just a bookkeeping issue. When total annual additions cross $72,000, the plan has to correct the excess. The typical fix is distributing the excess amounts plus earnings back to the participant. In some cases the plan reduces the affected participant’s future contribution limits to absorb the overage over time. These corrections are separate from the ACP test corrections above, and each has its own deadlines. The simplest defense is watching your running total during the year and coordinating with your plan administrator before December’s final payroll runs.

1
Internal Revenue Service. COLA Increases for Dollar Limitations on Benefits and Contributions
2
Office of the Law Revision Counsel. 26 USC 415 – Limitations on Benefits and Contribution Under Qualified Plans
3
Internal Revenue Service. Retirement Topics – 403(b) Contribution Limits
4
Office of the Law Revision Counsel. 26 US Code 415 – Limitations on Benefits and Contribution Under Qualified Plans
5
Internal Revenue Service. IRC 403(b) Tax-Sheltered Annuity Plans
6
Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
7
Internal Revenue Service. Application of IRC Section 415(c) When a 403(b) Plan Is Aggregated With a Section 401(a) Defined Contribution Plan
8
Internal Revenue Service. 403(b) Plans – Catch-Up Contributions
9
Internal Revenue Service. Guidance on Allocation of After-Tax Amounts to Rollovers
10
Internal Revenue Service. Rollovers of After-Tax Contributions in Retirement Plans
11
Internal Revenue Service. 401(k) Plan Fix-It Guide – The Plan Failed the 401(k) ADP and ACP Nondiscrimination Tests