Figuring out your tax return comes down to a straightforward sequence: add up your income, subtract your deductions, apply the tax rates to what’s left, then subtract any credits and payments you’ve already made. The final number tells you whether you owe more or you’re getting a refund. Here’s how each step works so you can follow the math yourself.
Step 1: Add Up All Your Income
Start by gathering every source of income you received during the year. For most people, the biggest number comes from a W-2, which your employer sends by late January showing your wages and the taxes already withheld. But income goes well beyond a paycheck. Freelance or contract work, interest from bank accounts, dividends from investments, rental income, unemployment benefits, and retirement distributions all count. Each of these typically arrives on its own form (various versions of the 1099), and the IRS gets a copy of every one.
Add all of these together and you get your total income, which appears on line 7b of Form 1040.
Step 2: Subtract Adjustments to Find Your AGI
Before you calculate the tax you owe, the tax code lets you subtract certain “above the line” adjustments from your total income. These include contributions to a traditional IRA, student loan interest (up to $2,500), health savings account contributions, and the deductible portion of self-employment tax if you’re freelancing. These adjustments are reported on Schedule 1 and flow onto line 10 of your 1040.
After subtracting them, you arrive at your adjusted gross income, or AGI. This number matters beyond just your return. It determines your eligibility for many credits, deductions, and even free filing options.
Step 3: Choose Your Deduction
Now you reduce your AGI further by taking either the standard deduction or itemized deductions, whichever is larger. Most filers take the standard deduction because it’s simpler and, for many households, bigger than the total of their itemizable expenses.
Itemizing makes sense if your combined mortgage interest, state and local taxes (capped at $10,000), charitable donations, and medical expenses above a certain threshold exceed the standard deduction amount for your filing status. You can run the numbers both ways to see which saves you more.
Some filers can also subtract a qualified business income deduction if they earn income through a pass-through business like a sole proprietorship, partnership, or S corporation. This deduction can be worth up to 20% of that qualified income and is calculated on Form 8995.
After subtracting your deductions, you land on line 15 of the 1040: your taxable income. This is the number the tax rates actually apply to.
Step 4: Apply the Tax Brackets
Federal income tax uses a marginal system, meaning different portions of your taxable income are taxed at different rates. You don’t pay one flat rate on everything. For tax year 2026, a single filer’s taxable income is taxed this way:
- 10% on the first $12,400
- 12% on income from $12,401 to $50,400
- 22% on income from $50,401 to $105,700
- 24% on income from $105,701 to $201,775
- 32% on income from $201,776 to $256,225
- 35% on income from $256,226 to $640,600
- 37% on income above $640,600
Married couples filing jointly get wider brackets. Their 10% bracket covers income up to $24,800, the 12% bracket runs to $100,800, and so on up to 37% on income above $768,700.
Here’s what this looks like in practice. Say you’re a single filer with $60,000 in taxable income. You’d pay 10% on the first $12,400 ($1,240), then 12% on the next $38,000 ($4,560), then 22% on the remaining $9,600 ($2,112). Your total federal tax would be $7,912, even though you’re “in the 22% bracket.” Your effective rate is about 13.2%.
Step 5: Subtract Credits
This is where many people confuse two concepts that work very differently. A deduction reduces your taxable income before tax rates are applied. A credit reduces the actual tax you owe, dollar for dollar. A $1,000 credit saves you $1,000 in tax regardless of your bracket, while a $1,000 deduction saves you only $220 if you’re in the 22% bracket.
Common credits include the child tax credit, the earned income tax credit for lower and moderate income workers, education credits like the American Opportunity Credit, and the child and dependent care credit. Some of these are “refundable,” meaning they can push your tax bill below zero and result in a payment to you even if you owed nothing.
After applying your credits, you have your total tax liability for the year.
Step 6: Compare What You Owe to What You’ve Paid
Throughout the year, you’ve likely already been paying toward your tax bill without thinking about it. If you have a job, your employer withheld federal income tax from every paycheck (the amount shown in box 2 of your W-2). If you’re self-employed, you may have sent quarterly estimated payments directly to the IRS.
Your refund or balance due is simply the difference between your total tax liability and what you’ve already paid. If your employer withheld $8,500 over the year and your actual tax comes out to $7,912, you get an $588 refund. If your withholding was only $7,000, you owe $912.
A large refund doesn’t mean you had a great tax year. It means too much was taken from your paychecks all year. You essentially gave the government an interest-free loan. You can adjust your withholding by submitting a new W-4 to your employer if you’d rather keep more in each paycheck and get a smaller refund.
Putting It All Together
Here’s the full formula in one place:
- Total income (wages + freelance + interest + everything else)
- Minus adjustments (IRA contributions, student loan interest, HSA contributions) = AGI
- Minus deductions (standard or itemized) = taxable income
- Apply tax brackets to taxable income = tax before credits
- Minus credits (child tax credit, education credits, etc.) = total tax owed
- Minus payments already made (withholding, estimated payments) = refund or balance due
How to Actually File
You can work through this math by hand using the 1040 instructions, but most people use software that handles the calculations automatically. The IRS offers two free options through its Free File program. If your AGI is $89,000 or less, you can use guided tax software from IRS partner companies at no cost for your federal return. If your income is above that threshold, Free File Fillable Forms are available at any income level, though they provide less guidance and are better suited for people comfortable with tax forms.
Paid software like TurboTax, H&R Block, and others walks you through the same logical sequence described above, asking questions and plugging your answers into the right lines. The underlying math is identical whether you use free or paid software, hire a preparer, or fill out the forms yourself. Understanding the steps means you can spot errors, make smarter decisions about withholding, and know exactly why your refund is the size it is.