A return can show zero regular income tax and still owe five figures. The "Other Taxes" block on Schedule 2 is where the Special Enrollment Examination (SEE) hides most of its computation points.
Form 1040 figures the taxpayer's regular income tax on line 16. Many taxpayers owe other taxes on top of that, and those go on Schedule 2, Additional Taxes. This lesson is organized around Schedule 2, so treat the schedule as your map.
Schedule 2 has two parts, and the part where each of these other taxes lands decides whether the taxpayer's credits can reduce it:
KEY: Nonrefundable credits reduce regular tax plus alternative minimum tax, added together. They do not reduce Part II taxes. So a taxpayer whose Form 1040 line 16 is zero can still owe thousands of dollars in Part II taxes.
The alternative minimum tax (AMT) is a second, parallel way of computing tax. You recompute income on a broader base, subtract a flat exemption, and apply two rates.
Common mistakes
- Pooling spouses for the Social Security wage base. The $176,100 base applies to each person, never to the return as a whole. On a joint return with two $150,000 salaries, each spouse pays full Social Security tax on their own salary, and neither spouse has excess social security withholding to recover.
- Refunding $10,924.20 instead of $10,918.20. The 2025 ceiling is $176,100 × 6.2% = $10,918.20. Wrong answer choices are built on the six-dollar arithmetic slip, so recompute the product rather than recalling it.
- Treating the qualified tips deduction as payroll relief. The OBBBA Schedule 1-A deduction of up to $25,000 reduces taxable income only. Tips are still subject to Social Security and Medicare tax, and unreported tips still draw the 50 percent §6652(b) penalty on Form 4137.
Bottom line
- Schedule 2 split: Part I alternative minimum tax is reduced by nonrefundable credits; Part II self-employment tax, household employment taxes, additional medicare tax, net investment income tax, and first-time homebuyer credit repayment are not.
- AMT 2025: exemption $88,100 single / $137,000 MFJ, phasing out 25 cents per dollar above $626,350 / $1,252,700; rates 26% then 28% above $239,100.
- Minimum tax credit: Form 8801, deferral items only, nonrefundable, carries forward indefinitely, never back.
- SE tax: net profit × 0.9235, then 12.4% to $176,100 and 2.9% unlimited; $400 floor, $108.28 for church employee income; half deductible.
Exam shortcut
Read the stem for the phrase "no regular tax" or "credits reduced tax to zero." That signals a Part II question and the answer is never zero. Sort every other-tax stem by three questions in order. Is there self-employment income? Multiply by 0.9235 first, always. Are there two thresholds in play?
The full lesson (about 8,479 words, 57 min read) adds 2 worked examples, all 7 common mistakes, a self-check, free in the app.
Learning objectives
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