A sole proprietor with $120,000 of net profit can move roughly $40,000 off the front page of the return before ever touching the standard deduction. Every dollar of it sits in the adjustments block.
Adjustments to income are subtractions taken early on the return. They are subtracted from gross income to reach adjusted gross income (AGI), and they're available whether or not you itemize. That timing is what makes them valuable: a lower AGI also widens dozens of downstream phase-outs, the income ranges where a credit or deduction shrinks as income rises.
On the 2025 return, three places matter for this topic, but only two of them actually hold adjustments to income:
KEY: Schedule 1-A deductions are not adjustments to income. They come off after AGI is figured and stack on top of the standard or itemized deduction. Because they never lower AGI, they never widen an AGI-based phase-out.
Self-employment tax is how a self-employed person pays Social Security and Medicare, since no employer is withholding those taxes from a paycheck.
Common mistakes
- Deducting 7.65% of net profit as the SE-tax adjustment. The shortcut skips the 92.35% step. On $96,000 of profit it gives $7,344, while the correct figure, half of the computed tax, is $6,782. Always compute the tax first, then halve it.
- Reducing Schedule SE by the health insurance or retirement deduction. Both are Schedule 1 items that lower AGI, not self-employment income. In Example 2, net earnings of $166,230 stay $166,230 for self-employment tax no matter how large the SEP contribution is.
- Deducting employer or cafeteria-plan HSA contributions. When $4,300 goes in through an employer or cafeteria plan, it has already escaped wages in Box 1. Deducting it again on Schedule 1 counts the same break twice.
Bottom line
- SE tax: net earnings are 92.35% of net profit, 15.3% up to $176,100 of combined wage base, 2.9% above; deduct exactly half.
- IRA: $7,000 plus $1,000 catch-up at 50, limited to earned compensation; single active-participant phase-out is $79,000 to $89,000 MAGI.
- Self-employed plans: SEP effectively 20% of net earnings after the half-SE-tax deduction, SIMPLE $16,500, solo 401(k) deferral $23,500, all inside $70,000.
- HSA: $4,300 self-only, $8,550 family, $1,000 catch-up at 55, fund by April 15, 2026; employer contributions are excluded, not deducted.
Exam shortcut
Read the adjustments block in computation order, because later lines depend on earlier ones. Self-employment tax first, then retirement and health insurance, then HSA, and student loan interest last, since its phase-out uses the AGI the others already lowered. Three stem signals decide most questions. "Eligible to participate in an employer plan" kills the self-employed health insurance deduction for those months even if the taxpayer declined coverage.
The full lesson (about 3,444 words, 23 min read) adds 2 worked examples, all 6 common mistakes, a self-check, free in the app.
Learning objectives
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