The Core Difference: When You Pay Taxes
With a traditional 403(b), you contribute pre-tax dollars now (reducing your taxable income this year) and pay ordinary income tax on withdrawals in retirement. With a Roth 403(b), you contribute after-tax dollars now (no immediate deduction) and pay zero tax on qualified withdrawals — including all the investment growth. Same contribution limit, completely different tax timing.
Traditional vs Roth 403(b) — key feature comparison
| Feature | Traditional 403(b) | Roth 403(b) |
|---|---|---|
| Contributions | Pre-tax (reduces taxable income now) | After-tax (no current deduction) |
| Growth | Tax-deferred | Tax-free |
| Withdrawals in retirement | Fully taxable as ordinary income | Tax-free (if age 59½+ and 5-year rule met) |
| Required Minimum Distributions | Required at age 73 | Required at 73 (unlike Roth IRA) |
| 2025 Contribution Limit | $23,500 ($31,000 if 50+) | Same — shared limit |
| Best for | Higher income now, lower income in retirement | Lower income now or expecting higher rates later |
The Break-Even Tax Rate
The math is simple: if your tax rate in retirement equals your tax rate today, traditional and Roth are equivalent in pure dollar terms. If your retirement tax rate is lower than today, traditional wins. If higher, Roth wins. The trick is estimating your retirement tax rate 20–30 years in the future — which requires looking at Social Security, pensions, and other income sources.
Side-by-Side Dollar Comparison
Assume a teacher earning $68,000 contributing $8,000/year for 30 years at 7% return. We compare traditional vs Roth assuming a 22% current bracket and 18% retirement effective rate:
Traditional vs Roth — same balance, different after-tax wealth at 22% now / 18% in retirement
| Traditional 403(b) | Roth 403(b) | |
|---|---|---|
| Annual contribution | $8,000 pre-tax | $8,000 after-tax ($6,240 effective cost) |
| Tax saved today (22%) | $1,760/year | $0 |
| Account balance at 30 years | $756,000 | $756,000 |
| Taxes on withdrawal (18%) | $136,000 (on full amount) | $0 |
| Net spendable wealth | $620,000 | $756,000 |
| Winner at 18% retirement rate | — | Roth wins by $136,000 |
Because retirement tax rates often end up higher than expected — from Social Security income, RMDs from traditional accounts, and potential future tax legislation — Roth tends to win in more scenarios than the simple bracket comparison suggests.
When Traditional Clearly Wins
Traditional is usually better when: you are in the 32%+ federal bracket today and expect to drop significantly in retirement; you live in a high-income-tax state and plan to retire in a no-tax state (Florida, Texas, Nevada); or you need the current-year deduction to qualify for deductions or credits that phase out at higher incomes.
When Roth Clearly Wins
Roth is usually better when: you are in the 12% or 22% bracket today; you are young and have decades of tax-free growth ahead; you want to leave tax-free assets to heirs; or you have significant other retirement income (pension + Social Security) that will push withdrawals into higher brackets.
The Split Strategy: Hedge Your Bets
Many financial planners recommend splitting contributions between traditional and Roth — especially for earners in the 22% bracket who face genuine uncertainty about retirement income. A 60/40 or 50/50 split gives you tax flexibility in retirement: draw from traditional in low-income years, from Roth when avoiding higher tax brackets.
If you get a raise that pushes you from 22% to 24%, shift more toward traditional. If you take a sabbatical or go part-time, shift more toward Roth to lock in the lower rate. The split is not a one-time decision.
Compare Traditional vs Roth 403(b) for Your Numbers
Run side-by-side projections with your salary, bracket, and expected retirement income to find your winner.