The difference between a 401(k) and a 403(b) comes down to who sponsors the plan and a handful of rules that follow from that. For-profit employers offer 401(k) plans; public schools, tax-exempt nonprofits, and churches offer 403(b) plans. Contribution limits, tax treatment, early-withdrawal penalties, and required minimum distributions are essentially the same. The real gaps show up in investment menus, a long-tenure catch-up that only 403(b) participants get, and whether the plan is covered by federal fiduciary rules.
Who Can Offer Each Plan
You don’t pick between the two. Your employer’s tax status does.
A 401(k) is for employees of private, for-profit businesses, from a two-person startup to a Fortune 500 company. It falls under Section 401 of the Internal Revenue Code.
A 403(b) is limited to a narrower set of sponsors: public schools (including K-12 districts and state universities), hospitals, charitable foundations, and other organizations that qualify as tax-exempt under Section 501(c)(3). Certain ministers also qualify, even some whose employers aren’t themselves tax-exempt, as long as they function as ministers in their day-to-day duties.1Internal Revenue Service. IRC 403(b) Tax-Sheltered Annuity Plans
If you move from a nonprofit to a for-profit employer, you’ll switch from one framework to the other. You can’t open either plan on your own.
Contribution Limits in 2026
The basic elective deferral limit is identical. For 2026, you can contribute up to $24,500 to a 401(k) or a 403(b). If you’re 50 or older, you can add an $8,000 catch-up, bringing your personal limit to $32,500.2Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
Counting employer matching and profit-sharing, total annual additions to your account can’t exceed $72,000 in 2026, or $80,000 if you’re 50 or older.3MissionSquare Retirement. 2026 Retirement Plan Contribution Limits That combined cap matters most if your employer offers a generous match.
Exceed the deferral limit in a single year (easy if you contribute to two plans) and the excess has to be distributed back to you by your tax return due date. Miss that deadline and the excess is taxed twice: in the year you contributed it, and again when it eventually comes out of the plan.4Internal Revenue Service. Consequences to a Participant Who Makes Excess Annual Salary Deferrals
The 15-Year Catch-Up (403(b) Only)
Here is where the two plans diverge on contributions. A 403(b) offers an extra catch-up that 401(k) plans don’t have. If you’ve worked for the same qualifying employer for at least 15 years, you may be able to contribute an additional amount equal to the smallest of three figures: $3,000, a $15,000 lifetime cap reduced by any prior use of this provision, or $5,000 times years of service minus all prior elective deferrals to the employer’s plan.5Internal Revenue Service. 403(b) Plans – Catch-Up Contributions
That third formula means the rule mostly helps long-tenured employees whose average annual deferrals have been below $5,000. The 15-year catch-up stacks on top of the age-50 catch-up, so a qualifying 403(b) participant can defer more than a 401(k) participant in the same year. In practice, the tenure requirement at a single employer is steep and the math often yields less than the full $3,000, but for a career teacher or hospital employee it’s worth running the numbers.
Investment Options and Fees
Most 401(k) plans offer a menu of mutual funds, index funds, target-date funds, and sometimes company stock. The employer picks the lineup; participants choose among those options. Because for-profit sponsors are involved, 401(k) plans face annual nondiscrimination testing to confirm that highly compensated employees aren’t benefiting disproportionately compared to rank-and-file workers.6Internal Revenue Service. 401(k) Plan Fix-It Guide – The Plan Failed the 401(k) ADP and ACP Nondiscrimination Tests Failing the tests can force refunds to higher-paid employees or additional employer contributions.
A 403(b) started life as a “tax-sheltered annuity,” and that origin still shapes the account. Participant accounts can be annuity contracts through an insurance company, custodial accounts invested in mutual funds, or, for church employees, retirement income accounts that offer both.1Internal Revenue Service. IRC 403(b) Tax-Sheltered Annuity Plans Annuity options can come with higher fees, surrender charges, and more complex fee disclosures than the fund menu you’d typically see in a 401(k). If you’re enrolling in an annuity-based 403(b), read the fee schedule carefully.
Many 403(b) plans, especially those sponsored by public schools and government entities, are exempt from the nondiscrimination testing 401(k) plans must pass.7Congressional Research Service. 403(b) Pension Plans – Overview and Legislative Developments Lighter compliance can mean lower administrative costs for the employer, but it also means less regulatory pressure to keep the plan equally useful to lower-paid workers.
ERISA and Fiduciary Protection
This is the gap that matters most to participants and gets the least attention.
Every 401(k) is covered by the Employee Retirement Income Security Act. ERISA imposes fiduciary duties on the people managing the plan, meaning they’re legally required to act in participants’ best interests, and it requires an annual Form 5500 filing with the Department of Labor that creates a public record of the plan’s finances.8U.S. Department of Labor. Employee Retirement Income Security Act (ERISA)9Internal Revenue Service. Form 5500 Corner
A 403(b) has a more complicated relationship with ERISA. Plans sponsored by public educational organizations and churches are exempt entirely. Private nonprofit 403(b) plans are generally subject to ERISA unless they meet a safe-harbor exemption that limits the employer’s role in the plan.7Congressional Research Service. 403(b) Pension Plans – Overview and Legislative Developments A non-ERISA plan doesn’t carry the same fiduciary protections, and participants may have fewer legal remedies if the plan is run poorly. All 403(b) plans still have to follow IRS rules on contribution limits and distribution timing regardless of ERISA status.
Practically: in a 401(k), there’s a legally required fiduciary watching the plan. In a 403(b) sponsored by a public school or church, that protection likely doesn’t apply, so the fee and investment review is on you.
Rules That Work the Same in Both Plans
Most of what people worry about is identical across the two.
Roth options. Both plans can offer a designated Roth account alongside pre-tax contributions. You pay income tax now, and qualified distributions come out tax-free. A distribution is qualified if you’ve held the account for at least five tax years (counted from January 1 of the year of your first Roth contribution to that plan) and you’re 59½, disabled, or deceased.10Internal Revenue Service. Retirement Topics – Designated Roth Account The $24,500 limit applies whether contributions are pre-tax, Roth, or a mix. Each employer plan has its own five-year clock; rolling into a new employer’s plan doesn’t carry it over.
Early withdrawals. Pull money before 59½ and you owe a 10% additional tax on top of income taxes.11Office of the Law Revision Counsel. 26 USC 72 – Annuities; Certain Proceeds of Endowment and Life Insurance Contracts The exceptions are broad and apply equally to both plans: separation from service at 55 or older, disability, death, substantially equal periodic payments, qualified birth or adoption (up to $5,000 per child), federally declared disasters (up to $22,000), emergency personal expenses (up to $1,000 per year), and domestic abuse (the lesser of $10,000 or 50% of your account). These waive the penalty only; regular income tax still applies to pre-tax distributions.
Loans and hardship withdrawals. Both plans can allow loans, though not every plan does. When permitted, you can borrow the lesser of 50% of your vested balance or $50,000, repaid with interest to your own account.12Internal Revenue Service. Retirement Topics – Loans Hardship withdrawals are separate, can’t be repaid, require an immediate and heavy financial need, and are capped at the amount needed; the IRS recognizes safe-harbor reasons including medical costs, a principal-residence purchase, tuition, eviction or foreclosure prevention, funeral expenses, and certain home repairs.13Internal Revenue Service. Retirement Topics – Hardship Distributions Hardship amounts are taxable and potentially penalized if you’re under 59½. A loan, where available, is almost always the better option because you repay yourself.
Vesting. Your own contributions are always 100% vested immediately in either plan. Employer contributions can vest over time, usually under cliff vesting (0% until three years of service, then 100%) or graded vesting (20% after two years, reaching 100% after six).14Internal Revenue Service. Retirement Topics – Vesting Factor this in before leaving a job.
Rollovers. If you change employers, pre-tax 401(k) balances can roll into a 403(b), pre-tax 403(b) balances into a 401(k), and either into a traditional IRA.15Internal Revenue Service. Rollover Chart Designated Roth balances can roll into another plan’s Roth account or into a Roth IRA. A direct trustee-to-trustee transfer avoids the 20% mandatory withholding on checks made out to you and the 60-day deadline that comes with an indirect rollover.
Required minimum distributions. You have to start taking RMDs at age 73 (rising to 75 for people born after 1959 under SECURE 2.0).16Internal Revenue Service. Retirement Topics – Required Minimum Distributions (RMDs) If you’re still working past your RMD age, most 401(k) and 403(b) plans let you delay distributions from that current employer’s plan until retirement; this doesn’t apply to former employers’ plans or to IRAs. Miss an RMD and the excise tax on the shortfall is 25%, dropping to 10% if corrected within the IRS window.17Office of the Law Revision Counsel. 26 USC 4974 – Excise Tax on Certain Accumulations in Qualified Retirement Plans SECURE 2.0 eliminated RMDs on designated Roth accounts inside employer plans starting in 2024.
What Changes in 2026 for Both Plans
Two SECURE 2.0 provisions take effect in 2026 and apply to 401(k) and 403(b) alike.
If you turn 60, 61, 62, or 63 during the year, your catch-up contribution limit rises to $11,250 instead of the standard $8,000.2Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500 Combined with the $24,500 base, that’s up to $35,750 in personal contributions. The higher amount drops back to the regular age-50 catch-up once you turn 64.
Starting in 2026, participants who earned $145,000 or more in FICA-taxable wages from the sponsoring employer in the prior year must make catch-up contributions on a Roth basis. Pre-tax catch-ups aren’t an option for these earners anymore. If the plan doesn’t offer a Roth account, affected employees can’t make catch-up contributions at all. The $145,000 threshold is based on your prior year’s W-2 from that specific employer.