Updated October 17, 2026. Quick answer: Line 9 adds the income lines and is your total income. Line 10 is the adjustments to income taken from Schedule 1, line 26. Line 11a subtracts line 10 from line 9 and is your adjusted gross income, and line 11b repeats that amount at the top of page 2.
Picking the Schedule C business code for your work (2025 chart): Schedule C business codes.
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IRS worksheets read line by line: EIC Worksheet A.
Business use of your home (Form 8829), the saver’s credit (Form 8880), clean vehicle credits (Form 8936) and amended returns (Form 1040-X), read line by line: Form 8880 line 12, Form 8936 Part I and Form 1040-X lines 1 to 3.
IRS worksheets from the 2025 Form 1040 instructions, read line by line: IRA Deduction Worksheet, Student Loan Interest Deduction Worksheet and Form 1040 worksheets.
Schedule D and Schedule E (Form 1040) for 2025, read line by line: Schedule D lines 16 and 17, Schedule E lines 20 to 22 and Schedule E Part III.
Schedule 8812 (child tax credit and additional child tax credit) for 2025, read line by line: Schedule 8812 line 3 and Schedule 8812 line 14.
Line-by-line IRS form guides for 2025: Form 2441 line 8, Form 2441 lines 10 and 11 and Form 8863 lines 1 to 8.
Schedule C and Schedule SE (Form 1040) for 2025, read line by line: Schedule C lines 14 and 15, Schedule C lines 27a to 29 and Schedule C line 30.
Form 8962 (premium tax credit) for 2025, read line by line: Form 8962 line 2a.
Schedule A and Schedule B (Form 1040) for 2025, read line by line: Schedule A line 5a, Schedule A line 15 and Schedule A line 16.
What the four lines say
Each of these four lines is defined by its caption on the form. The table quotes them.
| Line | Caption on the form |
|---|---|
| Line 9 | “Add lines 1z, 2b, 3b, 4b, 5b, 6b, 7a, and 8. This is your total income” |
| Line 10 | “Adjustments to income from Schedule 1, line 26” |
| Line 11a | “Subtract line 10 from line 9. This is your adjusted gross income” |
| Line 11b | “Amount from line 11a (adjusted gross income)” |
Line 8 is named inside the line 9 formula, as additional income from Schedule 1, but this page does not describe what Schedule 1 contains; that is on the Schedule 1 page. The rest of the return is mapped on Form 1040 line by line.
Line 9: total income
The form says “Add lines 1z, 2b, 3b, 4b, 5b, 6b, 7a, and 8. This is your total income”. In plain order, that is the amount from each income line the caption names: the line 1z page for wages and earned income, the lines 2a and 2b page for taxable interest, the lines 3a and 3b page for ordinary dividends, the lines 4a and 4b page for the taxable IRA amount, the lines 5a and 5b page for the taxable pension amount, the lines 6a and 6b page for taxable social security benefits, and the line 7 page for capital gain or loss.
Note which side of each pair the formula uses. It lists 2b, 3b, 4b, 5b and 6b, the taxable or ordinary amounts, and does not list 2a, 3a, 4a, 5a or 6a. The instructions’ check-your-math list also names the term: “Check your math, especially for the child tax credit, earned income credit (EIC), taxable social security benefits, total income, itemized deductions or standard deduction, taxable income, total tax, federal income tax withheld, and refund or amount you owe.”
Line 10: adjustments to income
The instructions give one sentence for this line, under the heading “Total Income and Adjusted Gross Income”: “Enter any adjustments to income from Schedule 1, line 26, on line 10.” The form caption is the same instruction in short form: “Adjustments to income from Schedule 1, line 26”. The number to copy is whatever Schedule 1 shows on its line 26.
Line 11a and line 11b: adjusted gross income
The form defines AGI on line 11a: “Subtract line 10 from line 9. This is your adjusted gross income”. Line 11b sits at the top of the second page under the heading for tax and credits, and its caption is “Amount from line 11a (adjusted gross income)”. The two lines carry the same amount.
A labelled illustration, not an IRS example, of the arithmetic the form defines, computed by subtraction: if line 9 were $62,000 and line 10 were $3,000, line 11a would be $62,000 minus $3,000, which is $59,000 and line 11b would repeat $59,000. These numbers are invented for the illustration.
Where AGI is used in the instructions
The instructions refer to line 11b in several places. One worksheet step says “Enter the amount from Form 1040 or 1040-SR, line 11b.”. The Student Loan Interest Deduction Worksheet instead says “Enter the amount from Form 1040 or 1040-SR, line 9”, so not every worksheet starts from the same line.
AGI also appears as a tiebreaker for qualifying children: “If the child lived with each parent for the same amount of time, the IRS will treat the child as the qualifying child of the parent who had the higher adjusted gross income (AGI) for 2025.”
Where the number comes from
Line 9 comes from the income lines above it, and line 10 comes from Schedule 1, line 26. Line 11a is arithmetic on those two, and line 11b copies line 11a. If you want to see where the tax on income is estimated, the 2025 tax brackets page shows the rate tables and the Schedule A page covers itemized deductions.
Where it goes next
The next step on the form uses line 11b: “Subtract line 14 from line 11b. If zero or less, enter -0-. This is your taxable income”. So AGI, from line 11b, is what the form subtracts deductions from to reach taxable income.
Edition and line numbers
This page reads the 2025 Form 1040 and its 2025 instructions. Those are the files irs.gov was serving as the current ones on 2026-10-17, and they are for the tax year 2025 return, filed in 2026. Check the tax year printed on the form in front of you and use the line numbers on that year’s form. For the 2025 edition, the instructions state: “The lines on Forms 1040 and 1040-SR are the same.” Line 11 is split into 11a on page 1 and 11b on page 2 in this edition; an earlier or later year’s form may number these differently, so go by the form you are filing.
Common mistakes
- Adding the wrong side of a pair into line 9. The caption lists “lines 1z, 2b, 3b, 4b, 5b, 6b, 7a, and 8”, not the ‘a’ lines.
- Entering a number on line 10 that is not Schedule 1, line 26. The instructions say “Enter any adjustments to income from Schedule 1, line 26, on line 10.”
- Treating line 11b as a new calculation. Its caption is “Amount from line 11a (adjusted gross income)”, a copy of line 11a.
Related: Schedule 1 Form 1040, 2025 tax brackets, Schedule A Form 1040, and Form 1040.
Sources
- Instructions for Form 1040 and Form 1040-SR (2025): https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
- Form 1040, U.S. Individual Income Tax Return (2025): https://www.irs.gov/pub/irs-pdf/f1040.pdf
Read from the IRS documents linked above on October 17, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.