What Is the Difference Between 401(a) and 403(b)?

The difference between a 401(a) and a 403(b) comes down to control: a 401(a) is an employer-controlled retirement plan where the employer sets the contribution rules and often makes participation mandatory, while a 403(b) is a voluntary savings plan where you choose how much to defer from your own paycheck. Both are used in the public and nonprofit sectors, both share the same $72,000 combined contribution ceiling for 2026, and both offer similar tax treatment. Where they part ways is in who can sponsor them, who decides what goes in, what the money can be invested in, and what catch-up options open up as you approach retirement.¹

Which Employers Can Offer Each Plan

A 401(a) is a qualified retirement plan most often sponsored by governmental employers: state agencies, municipalities, and public universities. Some nonprofits sponsor them too, though that is less common. The “401(a)” label refers to the broad section of the tax code that governs qualified employer trusts, so the familiar 401(k) is technically a subtype of 401(a) with a cash-or-deferred arrangement attached.²

A 403(b) has a narrower guest list. Only public schools, colleges and universities, churches, and organizations that hold tax-exempt status under Section 501(c)(3) can sponsor one. Cooperative hospital service organizations and certain ministers also qualify.³ Employers outside those categories simply cannot offer a 403(b).⁴

Many public employers offer both side by side. A state university, for example, might enroll you in a mandatory 401(a) and also open a voluntary 403(b) for additional savings.⁵

Who Decides How Much Goes In

This is the difference you feel every payday. In a 401(a) plan, the employer designs the contribution structure. The employer decides whether you must contribute, how much, and what it will put in on your behalf. Many governmental 401(a) plans require employees to contribute a fixed percentage of pay, with the employer adding a set match or flat amount. You generally cannot change your rate or opt out.

A 403(b) runs the other way. You decide whether to participate and how much to defer from your salary, up to the annual limit. Your employer may match or add a nonelective contribution, but the savings decision is yours. That voluntary structure is what makes a 403(b) feel like the nonprofit-sector cousin of the private 401(k).

2026 Contribution Limits

The annual limit on elective deferrals under Section 402(g) is $24,500 for 2026. This cap governs the salary deferrals you voluntarily direct into a 403(b) and also applies to 401(k) plans. It does not apply to mandatory “picked-up” contributions in a standalone 401(a) that has no cash-or-deferred feature.⁶ The $24,500 figure is per person across all eligible plans, not per plan. Contribute to both a 403(b) and a 401(k) in the same year and your combined elective deferrals still cannot exceed that single cap.⁷

The total annual addition limit under Section 415(c), which combines employee deferrals, employer matching, and employer nonelective contributions, is $72,000 for 2026 or 100% of compensation, whichever is less. This ceiling applies identically to 401(a) and 403(b) plans.¹⁸

Since 2024, employers sponsoring either plan can also make matching contributions when employees make qualifying student loan payments, even if the employee defers no salary. The match counts against the same $72,000 annual addition limit.⁹

Catch-Up Contributions

Both plans let participants aged 50 and older contribute extra. For 2026 the general catch-up is $8,000.⁷

Super Catch-Up for Ages 60 Through 63

Under the SECURE 2.0 Act, participants who are 60, 61, 62, or 63 during 2026 can contribute up to $11,250 in catch-up contributions instead of the standard $8,000. The higher limit applies to both 401(a) plans that include a 401(k) feature and to 403(b) plans.¹

The 403(b) 15-Year Service Catch-Up

The 403(b) has an extra catch-up that no 401(a) can offer. If you have worked at least 15 years for the same qualifying employer, such as a public school system, hospital, or church, you can add another amount on top of the age-based catch-up.¹⁰

The extra amount each year is the lowest of these three calculations:

$3,000
$15,000 minus the total 15-year catch-up amounts you have used in prior years
$5,000 multiplied by your years of service with the employer, minus all elective deferrals you have ever made to that employer’s plans

The lifetime cap is $15,000 per employer. Once you use it up, this catch-up is gone, though the age-based catch-up remains available separately.¹¹

Upcoming Roth Requirement for High Earners

Starting in 2027, catch-up contributions from employees who earned more than $150,000 in the prior year must be designated as Roth (after-tax) contributions. The rule applies to 401(k), 403(b), and governmental 457(b) plans. For 2026 it is not yet in effect, but plan sponsors are already preparing for the change.¹²

Investment Options

A 401(a) plan holds assets in a formal trust, which gives sponsors broad flexibility in choosing investments. Depending on the plan, options might include individual stocks, bonds, index funds, and target-date funds, much like a 401(k).²

A 403(b) is limited to two funding vehicles: annuity contracts from an insurance company, or custodial accounts invested exclusively in mutual funds. Church plans may also use retirement income accounts. This restriction often means a narrower menu than a 401(a), particularly where the plan leans on annuity products whose embedded fees can be hard to compare.⁴

Vesting

Vesting decides when you actually own the employer’s contributions to your account. Your own contributions, whether mandatory in a 401(a) or voluntary in a 403(b), are always immediately vested. The employer side is where the two plans diverge.

Governmental 401(a) plans can impose lengthy vesting periods on employer contributions, sometimes requiring 10 to 20 years of service before you fully own the employer’s share. Leave before vesting and you forfeit some or all of what the employer put in. A 403(b) match can also carry a vesting schedule, but these tend to be shorter, and many 403(b) plans vest employer contributions immediately. If you are weighing a job offer that includes a 401(a), the vesting schedule is one of the first things to check.

Rollovers Between the Two

Funds in a 401(a) can be rolled into a 403(b), a traditional IRA, another 401(a), or a 401(k), and the reverse works too. The IRS rollover chart treats 401(a) plans as qualified plans alongside 401(k) and profit-sharing plans, and all of these accept pre-tax rollovers from 403(b) plans.¹³ So if you move between a government job with a 401(a) and a nonprofit job with a 403(b), your savings can follow you without triggering a tax bill, as long as the rollover is done properly.

One caution for public safety employees. A special rule lets police officers, firefighters, EMTs, corrections officers, and other qualified public safety workers in a governmental plan avoid the 10% early withdrawal penalty after separating from service at age 50 or after 25 years of service, whichever comes first. Rolling the governmental balance into an IRA eliminates that exception.¹⁴ If you expect to need early access, keep the money in the employer plan.

Side-by-Side Comparison

The differences that matter most to a participant, in one place:

Sponsoring employers: 401(a) plans come mostly from governmental entities and some nonprofits; 403(b) plans are limited to public schools, 501(c)(3) organizations, and churches.
Contribution control: In a 401(a), the employer sets the structure and contributions are often mandatory. In a 403(b), the employee chooses how much to defer.
2026 elective deferral limit: $24,500 under Section 402(g), applying to 403(b) salary deferrals and to 401(k) plans. A standalone 401(a) without a 401(k) feature uses mandatory contributions not governed by 402(g).
2026 total contribution limit: $72,000 (or 100% of compensation) under Section 415(c), applying to both plan types.
Catch-up contributions: Both allow $8,000 for ages 50 and over, and $11,250 for ages 60 through 63. Only the 403(b) offers the additional 15-year service catch-up.
Investments: 401(a) trusts can hold a broad range of investments. 403(b) plans are limited to annuity contracts and mutual fund custodial accounts.
Vesting: Governmental 401(a) plans may require years of service before employer contributions are fully vested. 403(b) employee deferrals are always immediately vested.
Rollovers: Funds move freely between 401(a), 403(b), 401(k), and traditional IRA accounts.

For most public-sector and nonprofit employees, this is not really a choice you make. Your employer decides which plan to offer, and in many cases offers both. Knowing the differences tells you what to prioritize: check your vesting schedule inside a 401(a), push your elective deferrals in a 403(b), and if you have 15 or more years at the same qualifying employer, ask whether your 403(b) plan document allows the service-based catch-up before that extra room goes unused.

1
Internal Revenue Service. COLA Increases for Dollar Limitations on Benefits and Contributions
2
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3
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