Tax and Credits on Form 1040: From Line 16 to Total Tax

The Tax and Credits section on Form 1040, Lines 16 through 24, is where taxable income becomes an actual tax bill. Line 16 turns your taxable income into a base tax figure. Lines 17 through 22 add certain other taxes and subtract your nonrefundable credits. Line 23 layers in the taxes from Part II of Schedule 2. Line 24 adds it all up into your total tax for the year.¹

Here is the sequence in one glance:

Line 16: base tax from your taxable income and filing status.
Line 17: additional taxes from Schedule 2, Part I.
Line 18: Line 16 plus Line 17.
Line 19: Child Tax Credit or Credit for Other Dependents, from Schedule 8812.
Line 20: other nonrefundable credits from Schedule 3.
Line 21: Line 19 plus Line 20.
Line 22: Line 18 minus Line 21, or zero if credits exceed tax.
Line 23: other taxes from Schedule 2, Part II.
Line 24: Line 22 plus Line 23. Total tax.

Every figure on Lines 17 through 24 either traces back to a supporting schedule or is basic arithmetic. When something looks wrong in this part of the return, the fix is almost always on Schedule 2, Schedule 3, or Schedule 8812, not on the face of the 1040.

How Line 16 Turns Taxable Income Into Tax

Tax Table or Tax Computation Worksheet

If your taxable income is under $100,000, you look up your tax in the Tax Table published with the Form 1040 instructions. The table is organized by filing status and $50 income increments: find the row for your income, read across to your filing status column, and copy the amount to Line 16.² At $100,000 or above, you switch to the Tax Computation Worksheet and calculate the tax yourself using the seven federal bracket rates.

For 2026, single filers hit rates that run from 10% on the first $12,400 of taxable income up to 37% on income above $640,600. Married couples filing jointly get wider brackets: 10% up to $24,800, and 37% above $768,700.³ Each rate applies only to the income inside that bracket. A single filer with $60,000 in taxable income pays 10% on the first $12,400, 12% on the next $38,000, and 22% on the last $9,600.

Long-Term Capital Gains and Qualified Dividends

Long-term capital gains and qualified dividends don’t get taxed at the ordinary bracket rates. You run them through the Qualified Dividends and Capital Gain Tax Worksheet, which applies preferential rates of 0%, 15%, or 20% depending on total taxable income and filing status. For 2026, a single filer pays 0% on qualifying gains and dividends up to $49,450 of taxable income, 15% between $49,450 and $545,500, and 20% above that. For joint filers, the 15% rate starts at $98,900 and the 20% rate at $613,700.⁴

Skip this worksheet and you can overpay by thousands. Tax software handles it automatically. Anyone filing by hand needs to complete it separately and carry the result to Line 16.

The Kiddie Tax

If your dependent child has more than $2,700 in unearned income for 2026, Form 8615 taxes the excess at the parent’s marginal rate rather than the child’s rate.⁵ The rule generally covers children under 19, or under 24 for full-time students. The tax computed on Form 8615 flows into Line 16.

Line 17: Additional Taxes From Schedule 2, Part I

Part I of Schedule 2 captures two items, and the total transfers to Line 17.⁶

The first is the alternative minimum tax, calculated on Form 6251. AMT targets taxpayers who would otherwise pay little or no tax because of certain deductions and exclusions. For 2026, the AMT exemption is $90,100 for single filers and $140,200 for married couples filing jointly, phasing out starting at $500,000 and $1,000,000, respectively.³ If the exemption fully shelters you, Line 17 is zero.

The second is repayment of excess advance premium tax credits. If you got marketplace health insurance subsidies during the year and your actual income came in higher than what you estimated, the excess subsidy gets repaid here. Starting with tax year 2026, no caps apply to this repayment. The full excess must be returned regardless of income.⁷

Line 18 is simple addition: Line 16 plus Line 17.

Lines 19-21: Nonrefundable Credits

Nonrefundable credits reduce tax dollar for dollar, which makes them more valuable than deductions of the same size. A $1,000 deduction in the 22% bracket saves $220. A $1,000 credit saves the full $1,000. The tradeoff: nonrefundable credits can only bring your tax down to zero. Anything beyond that is lost.

Line 19: Child Tax Credit and Credit for Other Dependents

For 2026, the Child Tax Credit is worth up to $2,200 per qualifying child under age 17.⁸ Each child needs a Social Security number valid for employment, issued before the return’s due date.⁹ You calculate the credit on Schedule 8812 and carry the result to Line 19.

If you have dependents who don’t qualify for the Child Tax Credit because they’re 17 or older, or because they have an ITIN rather than an SSN, the Credit for Other Dependents may apply. That credit also flows through Schedule 8812 into Line 19.

An important note: $1,700 of the $2,200 Child Tax Credit is potentially refundable as the Additional Child Tax Credit. That refundable portion does not appear on Line 19. It shows up in the Payments section, later on the return. Only the nonrefundable portion sits on Line 19.

Line 20: Other Credits From Schedule 3

Schedule 3 collects credits that don’t have their own line on Form 1040. The most common ones are the foreign tax credit and the education credits (American Opportunity Credit and Lifetime Learning Credit) from Form 8863.¹⁰ These are totaled on Schedule 3, line 8, and that number moves to Line 20.¹¹

Line 21 adds Lines 19 and 20 together.

Line 22: The Nonrefundable Cap in Action

Line 22 subtracts Line 21 from Line 18. If credits exceed tax, Line 22 is zero, not a negative number. Suppose Line 18 is $3,000. Line 19 shows $2,200 in Child Tax Credit and Line 20 shows $1,500 in education credits, for $3,700 on Line 21. Line 22 is zero. The extra $700 disappears unless a specific credit has a refundable component (a portion of the American Opportunity Credit does, for instance), in which case that refundable piece surfaces elsewhere on the return. In most cases the excess cannot be carried into next year.

Line 23: Additional Taxes From Schedule 2, Part II

Part II of Schedule 2 is where self-employment tax lives. If you had freelance, contractor, or business income, Schedule SE calculates Social Security and Medicare taxes on your net earnings. The combined rate is 15.3%: 12.4% for Social Security up to the wage base, plus 2.9% for Medicare with no cap. Half of the self-employment tax is deductible as an adjustment to income earlier on the return, but the full tax lands here.⁶

Part II also holds the Net Investment Income Tax, a 3.8% surtax on investment income when modified adjusted gross income exceeds $200,000 for single filers, $250,000 for married filing jointly, and $125,000 for married filing separately.¹² These thresholds are not adjusted for inflation, so more taxpayers fall inside them each year. The tax applies to the lesser of your net investment income or the amount by which MAGI exceeds the threshold.

All of Part II’s taxes total on Schedule 2, line 21, which then transfers to Line 23.

Line 24: Your Total Tax

Line 24 is Line 22 plus Line 23. That number is your total federal tax liability for the year.¹

Line 24 is not what you owe at filing. The rest of the return subtracts payments you have already made, such as federal withholding, estimated tax payments, and refundable credits, from the Line 24 figure. If payments exceed Line 24, you get a refund. If they fall short, you owe the difference. Line 24 by itself represents the full cost of your federal income tax obligation before any payments are applied.

Where Refundable Credits Fit In

Refundable credits do not appear in the Tax and Credits section. They land in the Payments section, after Line 24. The distinction matters because refundable credits can push your balance below zero and generate a refund even when Line 24 is zero.

The two biggest refundable credits for most filers are the Earned Income Tax Credit and the Additional Child Tax Credit. For 2026, the EITC can be worth up to $8,231 for a family with three or more qualifying children, and workers without children may still qualify for a smaller amount.³ The Additional Child Tax Credit makes up to $1,700 per qualifying child refundable, limited by an earnings formula tied to income above $2,500.⁸

These credits are calculated on their own forms and entered later, but their impact on the bottom line depends on the numbers produced by Lines 16 through 24. An error anywhere in this section ripples through the rest of the return.

1
Internal Revenue Service. Form 1040 – 2025 U.S. Individual Income Tax Return
2
Internal Revenue Service. Publication 1040 – Tax and Earned Income Credit Tables
3
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
4
Internal Revenue Service. Revenue Procedure 2025-32
5
Internal Revenue Service. Topic No. 553, Tax on a Child’s Investment and Other Unearned Income (Kiddie Tax)
6
Internal Revenue Service. Schedule 2 (Form 1040) – Additional Taxes
7
Internal Revenue Service. Questions and Answers on the Premium Tax Credit
8
Office of the Law Revision Counsel. 26 USC 24 – Child Tax Credit
9
Internal Revenue Service. Child Tax Credit
10
Internal Revenue Service. Schedule 3 (Form 1040) – Additional Credits and Payments
11
Internal Revenue Service. About Form 1040, U.S. Individual Income Tax Return
12
Office of the Law Revision Counsel. 26 USC 1411 – Imposition of Tax