Additional Medicare Tax is 0.9% of Medicare wages above a filing-status threshold. It is not the 1.45% Medicare line on every stub.
The leftover most people miss at $300,000 is how far past $200,000 the single / other line already is. Joint is $250,000. Married filing separately is $125,000.
On $300,000 of Medicare wages:
- Single / other: excess $100,000 → tax $900
- Joint: excess $50,000 → tax $450
- Married filing separately: excess $175,000 → tax $1,575
- Single at exactly $200,000 → tax $0
The $200,000 single leftover is Additional Medicare at $200,000. Two jobs under the withholding trigger: $190,000 + $45,000 → $315 if single. Joint leftover: $260,000 → $90.
Hub: United States calculators.
Employers withhold the extra 0.9% once that W-2 crosses $200,000. They do not look at your joint return. A single filer at $300,000 on one job should see the extra line. Two $150,000 jobs can withhold $0 extra and you still owe $900 when you file single. Estimate, not tax advice.
Direct answer: $300,000 single → $900
- Single / other threshold = $200,000
- Excess = $300,000 − $200,000 = $100,000
- Tax = 0.9% × $100,000 = $900
- Same wages, joint = 0.9% × $50,000 = $450
- Same wages, MFS = 0.9% × $175,000 = $1,575
threshold = $250,000 joint · $125,000 MFS · $200,000 any other case
tax = 0.9% × max(0, Medicare wages − threshold)
Same $300,000, three statuses
| Status | Threshold | Excess | Tax |
|---|---|---|---|
| Single / other | $200,000 | $100,000 | $900 |
| Married filing jointly | $250,000 | $50,000 | $450 |
| Married filing separately | $125,000 | $175,000 | $1,575 |
Nearby single wages
| Single Medicare wages | Excess | Tax |
|---|---|---|
| $200,000 | $0 | $0 |
| $250,000 | $50,000 | $450 |
| $300,000 | $100,000 | $900 |
Base Medicare 1.45% is still on the whole wage. That is the FICA calculator, not this 0.9% add-on.
If one W-2 is $300,000, the extra 0.9% should start after that job crosses $200,000. Two jobs that each stay under $200,000 can withhold $0 extra and you still owe $900 on a single return.
No. NIIT is a different statute on net investment income. This page is wages only.