Form 1040 Explained: Every Line EA Candidates Need to Know

2026-07-10

Last reviewed: July 9, 2026. This article reflects current IRS rules and EA exam requirements as of this date.

Form 1040 is the center of the U.S. Tax system. If you pass the EA exam but can't read a 1040 cold, you're not ready. Here's what's on it and what the SEE tests.

The Structure

Form 1040 has a clear flow: income in, adjustments out, deductions applied, tax calculated, credits subtracted, payments compared. Two pages. Everything else is schedules.

Page 1. Income and Adjustments:

Line 1: Wages (from W-2)
Lines 2-3: Interest and dividends
Line 4: IRA distributions
Lines 5-6: Social Security, pensions/annuities
Line 7: Capital gains (from Schedule D)
Line 8: Other income (from Schedule 1)
Line 9: Total income
Line 10: Adjustments to income (from Schedule 1)
Line 11: Adjusted Gross Income (AGI)

AGI is the most important number on the return. Almost every phaseout and limitation uses AGI or modified AGI as the trigger. The EA exam tests AGI-dependent rules constantly: IRA deduction phaseouts, medical expense floor, passive loss allowance, education credits.

Page 2. Tax and Credits:

Line 12: Standard or itemized deduction
Line 13: Qualified business income deduction (§199A)
Line 15: Taxable income (AGI minus deductions)
Line 16: Tax (from tax tables or Schedule D worksheet)
Lines 19-21: Credits (child tax credit, other dependents, Schedule 3 credits)
Line 24: Total tax
Lines 25-32: Payments (withholding, estimated tax, refundable credits)
Line 34: Refund or Line 37: Amount you owe

What the EA Exam Tests

Filing status determines everything downstream. MFJ vs MFS tax rates differ. HoH has its own bracket.
The dependent rules for CTC, EITC, and HoH all cascade from earlier sections.
The difference between refundable and non-refundable credits matters for lines 31-33.
Estimated tax penalty rules: if you owe $1,000+ and don't meet a safe harbor, Form 2210 applies.
The "kiddie tax" appears on Form 8615 but flows to the parent's 1040 in certain cases.

Schedules Every EA Must Know

Schedule 1. Additional income (unemployment, alimony, gambling) and adjustments (IRA deduction, HSA, student loan interest, self-employed health insurance)
Schedule 2. Additional taxes (self-employment tax, additional Medicare tax, NIIT, household employment taxes)
Schedule 3. Additional credits and payments (foreign tax credit, education credits, residential energy credit, estimated tax payments)
Schedule A. Itemized deductions (medical, SALT, mortgage interest, charitable)
Schedule C. Sole proprietorship profit/loss
Schedule D. Capital gains and losses
Schedule E. Supplemental income (rental, K-1 pass-through)
Schedule SE. Self-employment tax

Common EA Exam Traps

Trap 1: Confusing above-the-line deductions (Schedule 1, reduce AGI) with itemized deductions (Schedule A, reduce taxable income). The distinction matters for AGI-dependent phaseouts.

Trap 2: The SALT cap. It's $10,000 ($5,000 MFS). It applies to the combined total of state income tax (or sales tax) plus property tax. The exam expects you to know which taxes count toward the cap.

Trap 3: Mortgage interest is deductible on up to $750,000 of acquisition debt (post-2017). Pre-2017 grandfathered debt has a $1,000,000 limit. The exam tests which limit applies.

Need to look up any of these forms? Check the IRS Form Lookup. Search by number or name. Purpose, filing rules, key sections, and EA exam relevance for 19 common forms.

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