The US federal income tax system taxes income progressively through five distinct steps. Understanding the sequence — and where reductions happen — is the key to accurately forecasting your tax bill and identifying legal ways to reduce it.
Step 1: Determine Gross Income
Gross income is every dollar received during the year from any source:
- W-2 wages and salary — your employer reports this on your W-2
- Self-employment and freelance income — reported on 1099-NEC or Schedule C
- Investment income — dividends, interest, capital gains
- Rental income — rent collected minus allowable expenses
- Other income — alimony received (pre-2019 agreements), gambling winnings, prize money
Money that does NOT count as gross income: gifts received, inheritances, life insurance proceeds, qualified Roth withdrawals.
Step 2: Subtract Above-the-Line Adjustments to Get AGI
Adjusted Gross Income (AGI) is gross income minus "above-the-line" deductions. You claim these on Schedule 1 regardless of whether you itemize — they are not affected by the standard deduction decision.
Key above-the-line adjustments:
- Traditional 401(k) contributions (up to $23,500 in 2026; $31,000 if age 50+)
- Traditional IRA contributions (up to $7,000; $8,000 if age 50+)
- HSA contributions (up to $4,300 single / $8,550 family in 2026)
- Student loan interest paid (up to $2,500, subject to income phaseout)
- Self-employed health insurance premiums
- Half of self-employment tax (SE tax paid on Schedule SE)
- Alimony paid (pre-2019 agreements only)
AGI matters beyond just taxes: it determines your eligibility for Roth IRA contributions, EITC, premium tax credits, and the deductibility of traditional IRA contributions.
Step 3: Subtract the Standard Deduction or Itemized Deductions
After reaching AGI, you subtract either the standard deduction or itemized deductions — whichever is larger. This produces taxable income, which is what the brackets actually apply to.
2026 Standard Deduction amounts:
| Filing Status | Standard Deduction |
|---|---|
| Single | $15,000 |
| Married Filing Jointly | $30,000 |
| Married Filing Separately | $15,000 |
| Head of Household | $22,500 |
| 65+ or blind (additional, per condition) | +$1,600 (single) / +$1,300 (MFJ) |
Itemized deductions (Schedule A) include:
- Mortgage interest on up to $750,000 of debt
- State and local taxes (SALT) — capped at $10,000 combined
- Charitable contributions (cash and non-cash)
- Medical expenses exceeding 7.5% of AGI
- Casualty losses in federally declared disaster areas
Since the TCJA doubled the standard deduction in 2018, roughly 90% of filers now take the standard deduction. Itemizing only wins if your Schedule A total exceeds the standard amount for your filing status.
Step 4: Apply the Tax Brackets Progressively
A common misconception: earning $50,000 does not mean you pay 22% on everything. The 22% bracket only applies to income within that bracket range. Each bracket taxes its own slice.
2026 Federal Tax Brackets — Single Filers:
| Rate | Income Range | Tax on This Slice |
|---|---|---|
| 10% | $0 – $11,925 | Up to $1,193 |
| 12% | $11,926 – $48,475 | Up to $4,386 |
| 22% | $48,476 – $103,350 | Up to $12,073 |
| 24% | $103,351 – $197,300 | Up to $22,548 |
| 32% | $197,301 – $250,525 | Up to $17,031 |
| 35% | $250,526 – $626,350 | Up to $131,511 |
| 37% | Over $626,350 | — |
Married Filing Jointly brackets are roughly double these thresholds at the lower end, collapsing near the top (the "marriage penalty" zone begins around $731,200 for the 37% bracket).
Step 5: Subtract Tax Credits
Credits reduce tax owed dollar-for-dollar — they are more valuable than deductions of the same amount because they come off the actual tax bill, not just taxable income.
Major 2026 tax credits:
| Credit | Maximum Value | Who Qualifies |
|---|---|---|
| Child Tax Credit | $2,000 per child under 17 | Phases out above $200K (single) / $400K (MFJ) |
| Earned Income Credit | Up to $7,830 | Low-to-moderate income earners with earned income |
| Child & Dependent Care | Up to $2,100 | Childcare costs enabling work |
| American Opportunity | Up to $2,500 | First 4 years of post-secondary education |
| Lifetime Learning | Up to $2,000 | Any post-secondary education or job training |
| Saver's Credit | Up to $1,000 | Low-income earners who contribute to retirement accounts |
Refundable credits (EITC, part of ACTC) can produce a refund even if you owe zero tax. Non-refundable credits can only reduce your bill to zero.
Worked Example: $85,000 Single Filer
| Step | Calculation | Amount |
|---|---|---|
| Gross income | W-2 wages | $85,000 |
| 401(k) contribution | Above-the-line adjustment | −$5,000 |
| AGI | $80,000 | |
| Standard deduction | Single filer 2026 | −$15,000 |
| Taxable income | $65,000 | |
| 10% bracket | $11,925 × 10% | $1,193 |
| 12% bracket | ($48,475 − $11,925) × 12% | $4,386 |
| 22% bracket | ($65,000 − $48,475) × 22% | $3,636 |
| Federal income tax | $9,215 | |
| Effective income tax rate | $9,215 ÷ $85,000 | 10.8% |
| Marginal rate | Highest bracket reached | 22% |
FICA taxes are calculated separately on gross wages (not taxable income): 6.2% Social Security + 1.45% Medicare = 7.65% × $85,000 = $6,503.
Total federal tax burden: $9,215 + $6,503 = $15,718 (18.5% of gross).
Marginal Rate vs. Effective Rate — Why It Matters
Your marginal rate is the bracket your last dollar falls into. Your effective rate is total tax ÷ total income. They are always different because the lower brackets apply to the first portions of income.
In the example above: marginal = 22%, effective = 10.8%. Knowing only the marginal rate dramatically overstates what you actually pay.
The marginal rate matters for one specific decision: whether an additional dollar of income (freelance work, Roth conversion, selling stock) is worth pursuing after tax. The effective rate is what matters for budgeting and comparing options.
What Reduces Your Total Tax Most
Ranked by typical impact:
- Maximize pre-tax retirement contributions — every $1,000 in a 401(k) saves $220–$370 depending on bracket, plus reduces FICA exposure if contributed pre-tax
- HSA contributions — triple tax-advantaged; reduce federal income tax, state tax, and FICA
- Claim all eligible credits — the EITC and Child Tax Credit are the largest transfers in the tax code
- Capital gains rate management — long-term gains are taxed at 0%, 15%, or 20% instead of ordinary income rates
- Harvest tax losses — realized investment losses offset gains dollar-for-dollar
Use our US Salary Tax Calculator to run your exact number — federal, state, and FICA — in one calculation.