Most people never see the actual calculation behind their tax bill. Software asks questions, a number appears, and you either get a refund or write a check. But the federal income tax follows a fixed sequence of steps, and once you know them you can predict your bill, check your withholding and see exactly what a raise, a 401(k) contribution or a new child does to it.
This guide walks through that sequence for tax year 2026, using the official figures from IRS Revenue Procedure 2025-32, which includes the changes made by the 2025 reconciliation law (the One, Big, Beautiful Bill Act). Every worked example below can be reproduced in our free Income Tax Calculator.
This guide is educational, not tax advice. It explains how the federal rules and the arithmetic work; your own return can involve rules not covered here. Check IRS instructions or a qualified tax professional before you file.
The six steps at a glance
- Gross income: wages, self-employment profit, interest, dividends, capital gains and other income.
- Adjusted gross income (AGI): gross income minus pre-tax 401(k) deferrals (already left out of your W-2), deductible IRA and HSA contributions, half of self-employment tax and similar adjustments.
- Deductions: the larger of the standard deduction or your itemized deductions, plus a few deductions available either way.
- Taxable income and the brackets: taxable income is run through the rate schedule for your filing status.
- Credits: subtracted dollar for dollar from the tax, such as the Child Tax Credit.
- Payments: total tax compared with what was withheld from your pay or paid in estimates. More paid means a refund; less means you owe.
Step 1 and 2: from gross income to AGI
Take Alex, a single filer earning an $80,000 salary who puts 6% ($4,800) into a Traditional 401(k). That contribution is taken out before income tax, so Alex's W-2 shows $75,200 of taxable wages in box 1. With no other income or adjustments, Alex's AGI is $75,200.
AGI matters beyond this return: many phase-outs, including the Child Tax Credit, the senior deduction and the tips and overtime deductions, are measured against it (or a close variant called modified AGI). That is one reason pre-tax retirement saving is so effective; see our guide on whether a 401(k) is worth it for the full picture.
Step 3: standard vs itemized deduction (2026 amounts)
You subtract whichever is larger: the standard deduction for your filing status, or your itemized deductions.
| Filing status | 2026 standard deduction | Extra if 65+ or blind (each) |
|---|---|---|
| Single | $16,100 | $2,050 |
| Married filing jointly | $32,200 | $1,650 |
| Married filing separately | $16,100 | $1,650 |
| Head of household | $24,150 | $2,050 |
Itemized deductions on Schedule A are mainly mortgage interest, state and local taxes (SALT), charitable gifts and medical costs above 7.5% of AGI. From 2026, charitable gifts only count to the extent they exceed 0.5% of your AGI. Two examples:
| Household | Mortgage interest | SALT | Charity (after 0.5% floor) | Itemized total | Standard | Better choice |
|---|---|---|---|---|---|---|
| Single, AGI $120,000 | $12,000 | $9,000 | $2,000 - $600 = $1,400 | $22,400 | $16,100 | Itemize (+$6,300) |
| Married jointly, AGI $150,000 | $14,000 | $12,000 | $4,000 - $750 = $3,250 | $29,250 | $32,200 | Standard |
The large standard deduction means most households, especially married couples, are better off not itemizing. If you take the standard deduction, from 2026 you can also deduct up to $1,000 of cash gifts to charity ($2,000 if married filing jointly) on top of it. Alex has no itemized deductions worth mentioning, so Alex takes the $16,100 standard deduction.
Step 4: taxable income and the marginal brackets
Alex's taxable income is $75,200 - $16,100 = $59,100. This is where the most common misunderstanding lives. The US uses marginal brackets: each rate applies only to the slice of income inside its band, not to all of your income. Here are the 2026 rate schedules from Rev. Proc. 2025-32:
| Rate | Single | Married filing jointly | Head of household |
|---|---|---|---|
| 10% | $0 to $12,400 | $0 to $24,800 | $0 to $17,700 |
| 12% | $12,400 to $50,400 | $24,800 to $100,800 | $17,700 to $67,450 |
| 22% | $50,400 to $105,700 | $100,800 to $211,400 | $67,450 to $105,700 |
| 24% | $105,700 to $201,775 | $211,400 to $403,550 | $105,700 to $201,750 |
| 32% | $201,775 to $256,225 | $403,550 to $512,450 | $201,750 to $256,200 |
| 35% | $256,225 to $640,600 | $512,450 to $768,700 | $256,200 to $640,600 |
| 37% | over $640,600 | over $768,700 | over $640,600 |
Alex's $59,100 is taxed slice by slice:
| Bracket | Income in this slice | Tax on the slice |
|---|---|---|
| 10% on $0 to $12,400 | $12,400 | $1,240 |
| 12% on $12,400 to $50,400 | $38,000 | $4,560 |
| 22% on $50,400 to $59,100 | $8,700 | $1,914 |
| Total | $59,100 | $7,714 |
Alex is “in the 22% bracket”, but only $8,700 is taxed at 22%. The effective rate is $7,714 / $75,200 = about 10.3% of total income, or 9.6% of the $80,000 gross salary. The marginal rate, the tax on the next dollar earned, is 22%.
The same method works at any income. A single filer with $300,000 of taxable income pays $1,240 + $4,560 + $12,166 (22% of $55,300) + $23,058 (24% of $96,075) + $17,424 (32% of $54,450) + $15,321.25 (35% of $43,775) = $73,769.25, an effective rate of about 24.6% on taxable income despite reaching the 35% bracket.
The raise myth: why more pay never means less take-home
A common worry is that a raise will “push you into a higher bracket” and leave you worse off. It cannot, because the higher rate applies only to the dollars above the threshold. Take a single filer whose taxable income rises from $50,000 to $51,000 with a $1,000 raise:
| Before raise | After raise | Change | |
|---|---|---|---|
| Taxable income | $50,000 | $51,000 | +$1,000 |
| Federal income tax | $5,752 | $5,932 | +$180 |
| FICA (7.65%) | +$76.50 | ||
| Extra take-home pay | +$743.50 |
$400 of the raise is taxed at 12% and $600 at 22%. The tax on the first $50,000 does not change at all. Where income can genuinely cost you more than it pays is in benefit and credit phase-outs (for example, the Additional Child Tax Credit for lower earners or means-tested benefits), not in the brackets.
Step 5: credits, including the 2026 Child Tax Credit
A deduction lowers taxable income; a credit lowers the tax itself, dollar for dollar, so a $1,000 credit is worth $1,000 to everyone while a $1,000 deduction is worth $220 in the 22% bracket. The biggest credit for most families is the Child Tax Credit:
- $2,200 per qualifying child under 17 for 2026
- Up to $1,700 per child is refundable (the Additional Child Tax Credit), limited to 15% of earned income above $2,500
- $500 credit for other dependents, such as older children or a parent you support
- Phases out by $50 per $1,000 of modified AGI above $200,000 ($400,000 married filing jointly)
Example: Sam and Jordan file jointly with $120,000 of wages, $6,000 of 401(k) contributions and two children. AGI is $114,000, taxable income is $114,000 - $32,200 = $81,800, and tax before credits is $2,480 (10% of $24,800) + $6,840 (12% of $57,000) = $9,320. The Child Tax Credit of $4,400 cuts that to $4,920.
The refundable part matters for lower incomes. A married couple earning $50,000 with two children has taxable income of $17,800 and tax of $1,780. The credit wipes out all $1,780, and the unused $2,620 comes back as a refundable credit (below the $3,400 cap for two children and the 15% earned-income limit of $7,125), so they can get money back even with no tax withheld.
Step 6: total tax vs withholding, refund or balance due
Your employer withholds income tax from each paycheck based on your W-4. At filing time, the return compares what you owe with what you paid:
| Alex (single) | Sam and Jordan (joint, 2 kids) | |
|---|---|---|
| AGI | $75,200 | $114,000 |
| Deduction | $16,100 | $32,200 |
| Taxable income | $59,100 | $81,800 |
| Tax from brackets | $7,714 | $9,320 |
| Credits | $0 | $4,400 |
| Total tax | $7,714 | $4,920 |
| Withheld during the year | $7,200 | $5,600 |
| Result | $514 owed | $680 refund |
A refund is not a bonus, just tax you overpaid; a balance due means withholding was too low. If the gap is large either way, adjust your W-4. Our Paycheck Calculator shows what each paycheck looks like after federal withholding, FICA, state tax and 401(k) deductions.
Capital gains are taxed on their own scale
Short-term gains (assets held a year or less) are taxed as ordinary income in the brackets above. Long-term gains and qualified dividends get lower rates, stacked on top of your ordinary taxable income. The 2026 thresholds are:
| Rate | Single | Married filing jointly | Head of household |
|---|---|---|---|
| 0% | up to $49,450 | up to $98,900 | up to $66,200 |
| 15% | $49,450 to $545,500 | $98,900 to $613,700 | $66,200 to $579,600 |
| 20% | over $545,500 | over $613,700 | over $579,600 |
Example: a single filer with $60,000 of wages and a $20,000 long-term gain has taxable income of $63,900. The ordinary part is $43,900, taxed at $5,020. The gain sits on top: the first $5,550 (up to $49,450) is taxed at 0% and the remaining $14,450 at 15%, or $2,167.50. Total tax: $7,187.50. Higher earners may also owe the 3.8% net investment income tax on investment income once modified AGI passes $200,000 ($250,000 joint).
FICA is a separate tax
Social Security and Medicare taxes (FICA) are not part of the income tax calculation and are not reduced by the standard deduction, credits or Traditional 401(k) contributions. For 2026, employees pay:
- 6.2% Social Security on wages up to $184,500 (the 2026 wage base set by SSA)
- 1.45% Medicare on all wages
- 0.9% Additional Medicare on wages above $200,000 ($250,000 joint)
Alex pays $4,960 + $1,160 = $6,120 of FICA on the full $80,000, on top of $7,714 of income tax. Self-employed people pay both halves, 15.3%, on 92.35% of net profit, and deduct half of it when working out AGI.
What changed for 2026 under the 2025 reconciliation law
The 2025 law made the 2017 bracket structure permanent and added several deductions, most claimed on the new Schedule 1-A. They are available whether or not you itemize, and they reduce taxable income, not AGI. At a high level, per the IRS summary:
| Provision | 2026 rule | Years |
|---|---|---|
| Senior deduction | Up to $6,000 per person 65+, reduced by 6% of modified AGI over $75,000 ($150,000 joint) | 2025 to 2028 |
| Qualified tips | Deduct up to $25,000; phases out above $150,000 modified AGI ($300,000 joint) | 2025 to 2028 |
| Overtime premium | Deduct the extra “half” of time-and-a-half pay, up to $12,500 ($25,000 joint), same phase-out | 2025 to 2028 |
| Car loan interest | Up to $10,000 of interest on a new passenger vehicle assembled in the US | 2025 to 2028 |
| SALT cap | $40,400 ($20,200 married separately), reduced above $505,000 modified AGI but not below $10,000 | Rises 1% a year through 2029 |
| Child Tax Credit | $2,200 per child, now indexed to inflation | Permanent |
The SALT figures come from the IRS's 2026 correction notice; the old cap was $10,000. Married couples filing separately cannot claim the senior, tips or overtime deductions.
Example: Pat, single and 68, has $90,000 of AGI. Pat's deduction is $16,100 + $2,050 (age 65+) = $18,150, plus a senior deduction of $6,000 - 6% of ($90,000 - $75,000) = $5,100. Taxable income is $90,000 - $18,150 - $5,100 = $66,750 and tax is $9,397. Without the senior deduction it would be $10,519, so the new rule saves Pat $1,122.
The short version
Income tax is a sequence, not a single rate: gross income, minus adjustments, equals AGI; minus deductions equals taxable income; the brackets turn that into tax one slice at a time; credits come off the tax; and withholding decides whether you get a refund. Your marginal rate tells you what the next dollar costs, your effective rate tells you what you pay overall, and FICA sits outside the whole calculation. Run your own numbers before the year ends, while there is still time to change your withholding or retirement contributions.
Frequently asked questions
How is federal income tax calculated, in one sentence?
Start with gross income, subtract pre-tax contributions and other adjustments to get AGI, subtract the standard or itemized deduction to get taxable income, run taxable income through the brackets, subtract credits, and compare the result with what was withheld from your pay to find your refund or balance due.
What are the 2026 federal tax brackets for a single filer?
10% on taxable income up to $12,400, 12% up to $50,400, 22% up to $105,700, 24% up to $201,775, 32% up to $256,225, 35% up to $640,600 and 37% above that. For married couples filing jointly the thresholds are $24,800, $100,800, $211,400, $403,550, $512,450 and $768,700.
Can a raise push me into a higher bracket and lower my take-home pay?
No. Only the dollars above a bracket threshold are taxed at the higher rate. A single filer whose taxable income rises from $50,000 to $51,000 pays $180 more federal income tax and $76.50 more FICA, so the $1,000 raise still adds $743.50 to take-home pay. Some credits and benefits phase out with income, but the brackets themselves never make a raise cost you money.
What is the standard deduction for 2026?
$16,100 for single filers and married filing separately, $32,200 for married couples filing jointly and $24,150 for heads of household. People 65 or older or blind add $2,050 each if unmarried or $1,650 each if married, and qualifying seniors can also claim the separate $6,000 senior deduction from 2025 to 2028.
How much is the Child Tax Credit in 2026?
Up to $2,200 per qualifying child under 17. Up to $1,700 per child is refundable as the Additional Child Tax Credit, limited to 15% of earned income above $2,500. The credit phases out by $50 for each $1,000 of modified AGI above $200,000, or $400,000 for married couples filing jointly.
Why do I owe tax when my employer withheld tax all year?
Withholding is only an estimate based on your W-4. You can owe if you have two jobs, a working spouse, side income, investment gains, or claimed fewer adjustments than your return shows. As a general rule the IRS does not charge an underpayment penalty if you owe less than $1,000 after withholding, but you still have to pay the balance by the filing deadline.
This guide is general information, not professional advice. Rates and rules change — check the official source before you file or sign anything. See our Disclaimer.