Form 8959: Additional Medicare Tax (2026)
The 0.9% surtax on high earners — and why withholding often misses it.
Form 8959 applies a 0.9% Additional Medicare Tax to combined wages and self-employment earnings above a filing-status threshold: $200,000 single and head of household, $250,000 married filing jointly, $125,000 married filing separately. Wages and self-employment income share ONE threshold — you do not get a separate allowance for each.
Who files Form 8959
- Employees whose wages exceed the filing-status threshold.
- Two-earner couples whose COMBINED wages exceed $250,000.
- Self-employed people whose net earnings exceed the threshold.
- Anyone whose employer withheld the surtax, to reconcile it.
Why couples get surprised by this
Employers must withhold the surtax once an individual's wages pass $200,000 — they have no way to know about a spouse. So a couple earning $150,000 each has $300,000 of combined wages, $50,000 over the $250,000 joint threshold, and zero withheld. The $450 lands at filing. This is one of the most common unexpected balances for dual-income households.
The thresholds are not indexed for inflation and are not the same as the Social Security wage base, so more households cross them each year.
Mixed wage and self-employment income
Wages are applied against the threshold first; only the remaining threshold shelters self-employment earnings. Someone with $150,000 of wages and $150,000 of self-employment profit does not get two $200,000 allowances — the wages consume $150,000 of the single threshold and most of the self-employment earnings are exposed. Self-employment earnings are measured after the 92.35% adjustment.
Frequently asked questions
Is there an employer match on the Additional Medicare Tax?
No. Unlike regular Medicare tax, the 0.9% surtax is employee-only. Employers withhold it but do not match it.
Why do I owe it when my employer withheld correctly?
Employers withhold based on your individual wages passing $200,000. For joint filers the threshold applies to combined income at $250,000, so a two-earner couple can owe it even when neither employer was required to withhold.
Are the thresholds indexed for inflation?
No. They have been fixed since the tax was introduced, so more taxpayers cross them over time.
Sources & verification
Last reviewed July 12, 2026.