401(k) vs 403(b)

The cleanest way to tell a 401(k) from a 403(b) is to look at the employer. A 401(k) is the retirement plan of the for-profit, private sector: companies large and small, from a corner startup to a Fortune 500 firm. A 403(b), sometimes called a tax-sheltered annuity, is the plan of tax-exempt and public-sector employers: public school systems, colleges and universities, hospitals, churches, and registered 501(c)(3) nonprofits.

You do not pick which one you get; your employer does. If you teach at a public school you almost certainly have access to a 403(b), and if you work at a software company you have a 401(k). That single fact, who your employer is, explains most of the structural differences that follow. The plans were written into different sections of the tax code for different kinds of organizations, and the small divergences below flow from that history.

On the numbers that matter most, the two plans line up. For 2026 the IRS set the employee elective deferral limit at $24,500 for both 401(k) and 403(b) plans, up from $23,500 in 2025. The age-50 catch-up contribution is $8,000, which brings a participant 50 or older to a total of $32,500. Under a SECURE 2.0 provision, participants aged 60, 61, 62, and 63 get a higher catch-up of $11,250 instead, for a total of $35,750.

The combined limit on everything that can go into the account in a year, your contributions plus any employer contributions, is $72,000 for 2026 under both plan types. One thing to watch: if you somehow participate in both a 401(k) and a 403(b) in the same year, your personal elective deferrals across the two are still capped at the single $24,500 base limit combined, not doubled. These figures change annually, so confirm the current numbers at IRS.gov before you set your contribution rate.

Here is a feature the 403(b) has and the 401(k) does not. If your 403(b) plan permits it and you have completed at least 15 years of service with the same eligible employer, such as a school system or hospital, you may be able to contribute up to an additional $3,000 per year on top of the standard limit, capped at $15,000 over your lifetime. It is meant to let long-tenured public and nonprofit employees catch up later in a career.

The mechanics are detailed: the extra amount is the lesser of several formulas, and when both the 15-year catch-up and the age-50 catch-up apply, the IRS requires deferrals above the standard limit to count against the 15-year catch-up first. Plans are not required to offer it, and the eligibility math trips people up, so confirm with your plan administrator before relying on it. A 401(k) has no equivalent provision.

This is where the practical experience of the two plans diverges most. A 401(k) typically offers a menu of mutual funds, and many plans include low-cost index funds and target-date funds. A 403(b) can offer the same, but historically its menus have leaned heavily on annuities and insurance-company products, a legacy of the plan's origins as a tax-sheltered annuity. Those products often carry higher fees, surrender charges, and layered costs that can quietly erode returns over decades.

The honest takeaway is that this is improving but uneven. Plenty of 403(b) plans now offer low-cost fund lineups comparable to a good 401(k), while others are still annuity-dominated. The only way to know is to read your plan's fee disclosure and the expense ratios of each option. If you have a 403(b), comparing the available funds and their costs is the single highest-value thing to check, more than any difference in the rules above.

A few more differences are worth knowing. ERISA, the federal law that sets fiduciary duties and reporting standards for retirement plans, almost always covers private-sector 401(k)s. Many 403(b) plans, particularly government and church plans, are exempt from ERISA, which can mean fewer of those built-in protections. Coverage varies by employer, so check your specific plan documents rather than assuming.

On employer match, both plans can offer one, but the match depends on the employer rather than the plan type. Many 401(k)s match part of your contributions; some 403(b)s do too, while other public-sector employers pair a 403(b) with a separate pension instead. And on taxes, both plans commonly offer a traditional pre-tax option and a Roth after-tax option. Traditional lowers your taxable income now and is taxed on withdrawal; Roth is funded with after-tax dollars and qualified withdrawals come out tax-free. Which fits depends on your situation, and this is not tax advice.

The pattern is clear: the rules are nearly identical, the offering employer differs, and the two real wrinkles are the 403(b) 15-year catch-up and the 403(b) tendency toward higher-fee annuity products. All 2026 figures above are worth confirming at IRS.gov, since the limits are adjusted each year. For background on each plan on its own, see our what is a 401(k) and what is a 403(b) guides.

The confusing part of these plans is rarely the headline limit; it is what you actually hold inside the account and what it costs you. A 403(b) annuity wrapper, a target-date fund's expense ratio, how concentrated your fund lineup is, how your balance is tracking against a broad market index: those are specific questions that an AI assistant can help you reason through when it can see your real holdings rather than a generic brochure.

That is where Walnut fits. It connects your existing brokerage through SnapTrade and lets you ask, in plain language through Claude, ChatGPT, or a built-in assistant, what you own, how each position is doing against the S&P 500, and where your costs are highest. It is read-only by default, and you approve any trade. Walnut is informational and is not a financial or tax advisor; it helps you see your own holdings, not tell you what to buy.

A 401(k) and a 403(b) are far more similar than different. They share the same 2026 contribution limits, the same catch-up amounts, the same combined employer-plus-employee cap, and the same traditional-and-Roth choice. The differences come down to who offers each (companies versus schools, nonprofits, churches, and hospitals), the 403(b)'s special 15-year catch-up, and ERISA coverage that more reliably protects 401(k)s. If you have a choice between two jobs, the plan type alone should rarely be the deciding factor.

The one thing genuinely worth scrutinizing is fees, especially in a 403(b) where annuity and insurance products have historically been common. Read the fee disclosure, compare the expense ratios, and contribute enough to capture any employer match. From a connected account you can dig into any ETF or individual stock your plan holds. All figures here are for 2026 and should be confirmed against the IRS, and none of this is tax advice.