Educational information, not individual financial advice.
Key Takeaways
These two rates answer different questions. Using the wrong one for a decision will mislead you.
Marginal tax rate is the tax rate applied to the next dollar you earn. If you're in the 22% bracket, your next $1 of income pays $0.22 in federal income tax. Your next $100 earned → $22 in tax. This is the rate that matters for decisions about whether to earn, save, or defer income.
Effective tax rate is the total federal income tax you pay divided by your total income. It's an average across all the bracket slices. For most taxpayers, it's substantially lower than the marginal rate.
Example: single filer, $120,000 taxable income (after deductions), 2026 brackets.
Showing a generic example — not your plan.
Your marginal rate applies only to the dollars earned inside that bracket. Your effective rate — what you actually pay as a % of total income — is always lower.
| Category | Value | Share |
|---|---|---|
| 10% bracket | $1,193 | 6% |
| 12% bracket | $4,386 | 20% |
| 22% bracket | $12,073 | 56% |
| 24% bracket | $3,996 | 18% |
Use marginal for decisions. Any question of the form "what does one more dollar do?":
Use effective for description. Questions of the form "how much am I paying in total?":
The most common misunderstanding of tax brackets is the belief that crossing into a higher bracket raises your tax on all income, causing a raise to leave you worse off. This is impossible. Only the income above the threshold is taxed at the higher rate.
Worked example: a taxpayer at $50,000 is in the 12% bracket. At $50,000 taxable income (in 2026 single filer, simplified), tax is roughly $5,680. A $1,000 raise pushes them slightly into the 22% bracket. Their tax on the first $50,000 is still $5,680. The tax on the additional $1,000 is 12% × the amount still in the 12% bracket + 22% × the amount in the 22% bracket — still leaving them with more take-home pay than without the raise.
Several quirks can push your effective marginal rate above your bracket:
Phase-outs. Tax credits and deductions often phase out as income rises. A child tax credit worth $2,000 can phase out $50 for every $1,000 of income above a threshold. Within the phase-out range, your marginal rate on that income isn't just the bracket — it's the bracket + the rate at which you're losing the credit.
ACA subsidies. For families buying health insurance on the exchange, going above certain income thresholds can eliminate subsidies worth thousands of dollars. Within that range, your effective marginal rate can be extreme.
Social Security taxation. For retirees, an additional $1 of other income can cause up to $0.85 of Social Security benefits to become taxable. Effective marginal rates in this "torpedo zone" can reach 40%+ even for retirees in the 22% bracket.
IRMAA (Income-Related Monthly Adjustment Amount). Medicare premiums go up at specific MAGI thresholds. Going $1 over a threshold can cost $1,500+ in additional annual Medicare premiums — effectively a massive marginal rate on that $1.
Your "true" marginal rate on earned income combines:
A middle-class Californian might face a combined marginal rate of 22% federal + 9.3% state + 7.65% FICA = 38.95% on their next dollar of earned income. The effective rate is lower because the brackets below apply lower rates.
High-earners benefit more from pre-tax contributions. A 401(k) contribution saves taxes at your marginal rate. If you're at 35% federal + 6% state = 41% marginal, a $10,000 Traditional contribution saves you $4,100 in tax. The same contribution for someone at 12% federal + 0% state saves $1,200.
Roth conversions should happen in low-bracket years. Converting $50,000 of Traditional to Roth when you're in the 12% bracket (possibly an early-retirement year before Social Security starts) costs $6,000. The same conversion in your peak earnings at 32% costs $16,000. The difference is pure value created by timing.
Horizons uses marginal rates for the tax gross-up math in retirement withdrawals — when you need to cover a spending shortfall from a pre-tax account, the engine withdraws enough to cover both the shortfall and the tax on the additional income, calibrated to your current marginal rate. Monte Carlo scenarios can include tax rate changes, so you can see how plans hold up under different future tax environments.
You're deciding whether to contribute another $1,000 to your Traditional 401(k). Your effective rate is 14%, and your marginal rate is 24%. Which rate should drive the decision?
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