Schedule 1-A walkthrough.

What Schedule 1-A is

Schedule 1-A (Form 1040), Additional Deductions, is the 2025 form that collects four deductions in one place and sends the total to Form 1040 or 1040-SR line 13b (Form 1040-NR line 13c). The IRS form has six parts: Part I works out your modified adjusted gross income, Part II is no tax on tips, Part III is no tax on overtime, Part IV is car loan interest, Part V is the enhanced deduction for seniors and Part VI adds the four results on line 38. This page follows the 2025 form, the one used on returns filed in 2026.

Part I: the income number everything else uses

Line 1 is the amount from Form 1040 line 11b. Lines 2a to 2d add back certain excluded income: Puerto Rico income you excluded and amounts from Forms 2555 and 4563. Line 3 adds line 1 and line 2e, and that line 3 amount is the MAGI used in every later part. The calculator asks for it directly.

Part II and Part III: tips and overtime

For tips, line 7 is the smaller of your qualified tips (line 6) or $25,000. For overtime, line 15 is the smaller of qualified overtime compensation (line 14c) or $12,500, or $25,000 if married filing jointly. Both reduce when MAGI passes $150,000, or $300,000 if married filing jointly: subtract the threshold, divide by $1,000 and round down to a whole number, multiply by $100, and subtract that from the capped amount. The form warns that if you are married you must file jointly to claim the tips and overtime deductions, and that you and your spouse need valid Social Security numbers.

Part IV: car loan interest

Line 24 is the smaller of your qualified passenger vehicle loan interest or $10,000. The reduction starts above $100,000 of MAGI ($200,000 if married filing jointly): subtract the threshold, divide by $1,000 and round up to the next whole number, then multiply by $200. Note the direction: tips and overtime round down, car loan interest rounds up.

Part V: seniors

The enhanced deduction for seniors starts at $6,000. MAGI above $75,000 ($150,000 if married filing jointly) cuts it by 6 percent of the excess. Line 36a applies to you if you have a valid Social Security number and were born before January 2, 1961, and line 36b to your spouse if you file jointly and your spouse meets the same test, so a couple can claim it twice.

Worked examples

Single, MAGI $120,000, tips $8,000, overtime $5,000, car loan interest $6,000, no senior deduction. Tips and overtime are under the $150,000 threshold, so line 13 is $8,000 and line 21 is $5,000. For the car loan, $120,000 - $100,000 = $20,000, divided by $1,000 is 20, times $200 is $4,000, so the deduction is $6,000 - $4,000 = $2,000. Line 38 is $8,000 + $5,000 + $2,000 = $15,000.

Single, MAGI $160,000, tips $10,000. The excess over $150,000 is $10,000, divided by $1,000 is 10, times $100 is $1,000, so the tips deduction is $9,000. A single person born before January 2, 1961 with MAGI $100,000 has $25,000 over $75,000, 6 percent is $1,500 and the senior deduction is $4,500.

Method

The calculator follows the 2025 Schedule 1-A line by line: the caps, the phase-out subtraction, the rounding direction in each part and the $6,000 senior amount for each qualifying person on a joint return. It does not decide whether an item qualifies; the form's instructions, the tipped-occupation list and vehicle rules do.

What this does not cover

• Which occupations or vehicles qualify; read the IRS instructions.
• How Form W-2, 1099 and 4137 amounts feed lines 4 and 5 and 14.
• State treatment of these deductions.
• Tax year 2026, for which the form is not yet published as of this date.

Figures read from the sources below on November 11, 2026. Last updated November 11, 2026.

Sources

• IRS: Schedule 1-A (Form 1040), Additional Deductions, 2025 (retrieved November 11, 2026)