How to Calculate Tax Liability: Brackets, Surtaxes & Credits

To calculate your federal tax liability, add up all your income, subtract the adjustments and deductions the tax code allows, apply the tax brackets to what remains, add any extra taxes you owe, and then subtract your credits. For the 2026 tax year, that runs through seven brackets from 10% to 37%, with a standard deduction of $16,100 for single filers and $32,200 for married couples filing jointly.¹ Each step below shows where your number comes from.

Start With Gross Income

Gross income is every dollar you received during the year: wages, freelance and contract pay, interest, dividends, capital gains, rental income, retirement distributions, gambling winnings, alimony from a pre-2019 agreement, and side-business earnings. For W-2 employees, Box 1 of Form W-2 shows taxable wages after pre-tax retirement contributions and certain benefits are removed.² Freelance income appears in Box 1 of Form 1099-NEC.

Investment income arrives on separate forms: 1099-INT for bank and bond interest, 1099-DIV for dividends (Box 1a ordinary, Box 1b qualified), and 1099-B for proceeds from selling stocks or other assets. Add every source together. That total is your gross income, and each step that follows works to shrink it before rates apply.

Subtract Adjustments to Get Your AGI

Adjusted gross income is gross income minus the “above-the-line” adjustments claimed on Schedule 1 of Form 1040. You get these whether you take the standard deduction or itemize. AGI also decides your eligibility for a long list of other tax benefits, so this figure matters beyond the immediate calculation.

The adjustments most people use:

Educator expenses, up to $300 in unreimbursed classroom costs for eligible teachers.³
Student loan interest, up to $2,500, phasing out for single filers with modified AGI between $85,000 and $100,000 and joint filers between $175,000 and $205,000.⁴
Traditional IRA contributions up to $7,500, or $8,600 if you’re 50 or older, with a phase-out at higher incomes if you or your spouse have a workplace plan.⁵
Half of your self-employment tax, if you’re self-employed.⁶
Contributions to a health savings account, if you’re enrolled in a qualifying high-deductible health plan.

Subtract every adjustment you qualify for from gross income. The result is your AGI. It lands on line 11 of Form 1040.

Subtract the Standard or Itemized Deduction

Next, take out either the standard deduction or your total itemized deductions, whichever is larger. Filing status sets the standard amount. For 2026:¹

Single or married filing separately: $16,100
Married filing jointly: $32,200
Head of household: $24,150

Most filers take the standard deduction because it’s simple and often the larger figure. Itemizing on Schedule A is worth the effort when qualifying expenses exceed the standard amount.⁷ The items most likely to push you over are mortgage interest on your primary home, state and local taxes (capped at $10,000), medical costs above 7.5% of AGI, and charitable contributions.

What’s left after this subtraction is your taxable income. That’s the figure you actually run through the brackets.

Apply the 2026 Federal Tax Brackets

Federal income tax is progressive. Your taxable income gets stacked into layers, and only the dollars sitting inside each layer are taxed at that layer’s rate. Moving into a higher bracket does not push all your income up to the higher rate; it only affects the dollars above the threshold. Here are the 2026 brackets for single filers:¹

10%: $0 to $12,400
12%: $12,401 to $50,400
22%: $50,401 to $105,700
24%: $105,701 to $201,775
32%: $201,776 to $256,225
35%: $256,226 to $640,600
37%: Over $640,600

Married couples filing jointly get brackets roughly twice as wide at the lower rates: $24,800 for the 10% bracket, $100,800 for the 12% bracket, and so on.¹

A Worked Example

A single filer with $60,000 in taxable income owes:

First $12,400 × 10% = $1,240
Next $38,000 (from $12,401 to $50,400) × 12% = $4,560
Remaining $9,600 (from $50,401 to $60,000) × 22% = $2,112

Total federal income tax before credits: $7,912. The top bracket is 22%, but the effective rate is about 13.2% ($7,912 ÷ $60,000). That gap between marginal and effective rate is the whole point of the progressive structure.

Handle Capital Gains and Qualified Dividends Separately

Not all income runs through those seven brackets. Long-term capital gains (on assets held longer than a year) and qualified dividends are taxed at preferential rates of 0%, 15%, or 20%, depending on total taxable income. For 2026, a single filer pays 0% on these gains up to roughly $49,450 in taxable income, 15% up to about $545,500, and 20% above that.

Short-term capital gains, on assets held a year or less, don’t get the break. They run through the ordinary brackets like wages. If you sold investments during the year, sort them by holding period before working them into the calculation, or your numbers will be off.

Add Self-Employment Tax If It Applies

Freelance, sole-proprietor, and partnership income carries self-employment tax on top of income tax. It covers the Social Security and Medicare contributions an employer would otherwise split with you. The combined rate is 15.3%: 12.4% for Social Security and 2.9% for Medicare.⁸

The Social Security portion applies only to the first $184,500 of net self-employment earnings in 2026.⁹ The Medicare portion has no cap. Before calculating the tax, reduce net self-employment income by 7.65% to approximate the employer-share deduction W-2 workers get automatically. Multiply the result by 15.3%.

Then remember the piece people miss: half of your self-employment tax comes back as an above-the-line adjustment when you calculate AGI.⁶ Miss that deduction and you’ll overstate your income tax.

Add the Surtaxes If Your Income Is High

Two extra taxes can layer on top of your regular income tax and self-employment tax. Both use the same thresholds, and those thresholds do not adjust for inflation.

Net Investment Income Tax

If your modified AGI exceeds $200,000 (single) or $250,000 (married filing jointly), you owe 3.8% on the smaller of your net investment income or the amount your modified AGI exceeds the threshold.¹⁰ Net investment income covers interest, dividends, capital gains, rental income, and royalties. It does not include wages or self-employment earnings.

Additional Medicare Tax

An extra 0.9% Medicare tax applies to wages and self-employment income above $200,000 for single filers or $250,000 for joint filers.¹¹ Employers start withholding it automatically once wages cross $200,000 in a calendar year, regardless of filing status. Married joint filers whose combined wages don’t actually exceed $250,000 can recover the over-withholding when they file. Self-employed workers calculate and pay it themselves.

Subtract Your Credits

With your total tax added up (brackets plus self-employment tax plus any surtaxes), subtract your credits. Credits are more valuable than deductions dollar for dollar: a $1,000 deduction saves you $220 in the 22% bracket, but a $1,000 credit saves you the full $1,000. Nonrefundable credits reduce tax to zero but no further. Refundable credits can generate a payment from the IRS even after tax hits zero.

The credits most filers encounter:

Child Tax Credit, up to $2,200 per qualifying child under 17 for 2026, partly refundable, phasing out at $200,000 modified AGI for single filers and $400,000 for joint filers.¹²
Earned Income Tax Credit, fully refundable, reaching $8,231 for a family with three or more qualifying children in 2026. Filers without children can qualify for a smaller credit.¹
Education credits: the American Opportunity Credit (up to $2,500 per student for the first four years of college) and the Lifetime Learning Credit (up to $2,000 per return).
Energy credits for home efficiency improvements, electric vehicles, and residential solar.

Subtract your total credits from your calculated tax. Any refundable credits remaining after tax reaches zero become part of your refund. What’s left is your final federal tax liability.

Compare Your Liability to What You’ve Already Paid

Your liability is what you owe for the year. Your payments are what you’ve already sent in through withholding and estimated payments. The difference between the two is your refund or balance due, and Form 1040 does the comparison for you. Line 24 is your total tax. Line 33 is your total payments, including W-2 withholding, quarterly estimated payments, and refundable credits. If line 33 is larger, the difference is your refund. If line 24 is larger, you owe the difference.¹³

A large refund means too much was withheld during the year. A large balance due means too little was withheld, and depending on the size, you could face an underpayment penalty. Getting close to zero in either direction is the target.

State Tax Is a Separate Calculation

Everything above is federal only. Most states impose their own income tax, with rates ranging from a flat percentage to graduated brackets reaching nearly 12% in the highest-tax states. Nine states have no personal income tax. Each state has its own rules for deductions, credits, and filing, so your total tax picture requires a separate state-level calculation after the federal one is done.

1
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
2
Internal Revenue Service. About Form W-2, Wage and Tax Statement
3
Internal Revenue Service. Topic No. 458, Educator Expense Deduction
4
Office of the Law Revision Counsel. 26 U.S. Code 221 – Interest on Education Loans
5
Internal Revenue Service. 401(k) Limit Increases to $24,500 for 2026, IRA Limit Increases to $7,500
6
Office of the Law Revision Counsel. 26 U.S. Code 164 – Taxes
7
Internal Revenue Service. About Schedule A (Form 1040), Itemized Deductions
8
Office of the Law Revision Counsel. 26 U.S. Code 1401 – Tax on Self-Employment Income
9
Social Security Administration. Contribution and Benefit Base
10
Office of the Law Revision Counsel. 26 U.S. Code 1411 – Imposition of Tax
11
Internal Revenue Service. Topic No. 751, Social Security and Medicare Withholding Rates
12
Internal Revenue Service. Child Tax Credit
13
Internal Revenue Service. Form 1040, U.S. Individual Income Tax Return