Updated October 18, 2026. Quick answer: Part II of Form 8959 figures the Additional Medicare Tax on self-employment income. It starts from Schedule SE, reduces the filing status amount by the Medicare wages carried from line 4, and multiplies any excess by 0.9%. The result on line 13 carries to Part III.
What this part is for
Part II is for people with self-employment income, as the instructions put it: “didn’t have” self-employment “income, skip Part II and go to Part III.” It sits inside Form 8959, right after Form 8959 Part I.
The instructions explain how wages and self-employment income interact: “Medicare wages and” self-employment “income are combined to determine if your income exceeds the threshold.” A self-employment “loss shouldn’t be considered for purposes of this tax.”
The lines, one by one
| Line | What the form says |
|---|---|
| 8 | Self-employment “income from Schedule SE (Form 1040), Part I, line 6. If you” “had a loss, enter” “-0-“. |
| 9 | “Enter the following amount for your filing status:” The form prints the same filing status amounts as on line 5. |
| 10 | “Enter the amount from line 4” |
| 11 | “Subtract line 10 from line 9. If zero or less, enter” “-0-“. |
| 12 | “Subtract line 11 from line 8. If zero or less, enter” “-0-“. |
| 13 | Additional Medicare Tax on self-employment “income. Multiply line 12 by 0.9% (0.009). Enter here and” “go to Part III”. |
Where the number comes from
Line 8 comes from Schedule SE: “Enter your” self-employment “income from Schedule SE (Form 1040), Part I, line 6.” “Combine amounts from this line if you have multiple Schedules SE.” To see how that Schedule SE line is built, read Schedule SE lines 1 to 4 and self-employment tax explained.
Lines 9 to 11 apply the wage rule from the instructions: “If you have both wages and” self-employment “income, the threshold amount for applying Additional Medicare Tax on the” self-employment “income is reduced (but not below zero) by the total amount of Medicare wages received.” Line 10 is how the form brings the wages in: “Enter the amount from line 4”.
Line 13 is described this way in the instructions: “Multiply line 12 by 0.9% (0.009).” “Enter the result on this line and go to Part III.”
Where it goes next
Line 13 flows into Part III, covered in Form 8959 Part III, and from there into the total on Form 8959 Parts IV and V. Compare the wider rules in Additional Medicare Tax.
A worked example
Illustration, not an IRS example. The inputs are invented, and the line 9 amount is a stand-in chosen only for easy arithmetic; it is not the amount printed for any filing status. Line 10 assumes line 4 was 50,000.
| Line | Amount in the illustration |
|---|---|
| Line 8 | $60,000 (invented, for the computation) |
| Line 9 (stand-in) | $80,000 (invented, for the computation) |
| Line 10 (from line 4) | $50,000 (invented, for the computation) |
| Line 11 | $30,000 (computed) |
| Line 12 | $30,000 (computed) |
| Line 13 | $270 (computed) |
Line 11 is 80,000 minus 50,000, which is 30,000. Line 12 is 60,000 minus 30,000, which is 30,000. Line 13 is 30,000 x 0.009, which is 270.
Edition and line numbers
This page reads Form 8959 for 2025 and its 2025 instructions, the current files irs.gov served on 2026-10-18. Check the edition printed on your own form and use that edition’s line numbers.
Common mistakes
- Putting a loss on line 8. The form says “had a loss, enter” “-0-“, and the instructions add that a self-employment “loss shouldn’t be considered for purposes of this tax.”
- Skipping line 10. The wage amount reduces the room on the self-employment side, because “is reduced (but not below zero) by the total amount of Medicare wages received.”
- Using only one Schedule SE. The instructions say “Combine amounts from this line if you have multiple Schedules SE.”
Related: Form 8959, Additional Medicare Tax, Schedule SE, Schedule SE lines 1 to 4, and self-employment tax explained.
Sources
- Form 8959 (2025), Additional Medicare Tax: https://www.irs.gov/pub/irs-pdf/f8959.pdf
- 2025 Instructions for Form 8959: https://www.irs.gov/pub/irs-pdf/i8959.pdf
- IRS: About Form 8959: https://www.irs.gov/forms-pubs/about-form-8959
Read from the IRS documents linked above on October 18, 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.