US Payroll & Self-Employment Tax Navigator
Self-Employment Tax, Excess Social Security Tax, Additional Medicare Tax. Diagnose complex tax issues and simulate savings strategies all in one place.
Calculate your Self-Employment Tax based on net business profit and see the impact of various deductions.
Income & Expenses (2025 Basis)
Savings Strategies (AGI Deductions)
SE Tax Calculation Results
Did you receive a W-2 from two or more employers? Check for overpaid Social Security tax and calculate your refundable credit.
W-2 Information (2025 Basis)
2025 Max Social Security Tax:
(based on wage base limit of )
Refund Calculation Results
Your Refundable Credit
$0.00
Calculate your Additional Medicare Tax liability as a high-earner and see the effect of savings strategies.
Income Information
Income can be linked automatically from the SE Tax simulator.
Additional Medicare Tax (AMT) Results
Estimated Additional Medicare Tax (0.9%)
$0.00
Threshold: $0
Comprehensive Information & FAQ
Self-Employment (SE) Tax Key Summary
Composition: Social Security (12.4%) + Medicare (2.9%) = 15.3%.
Calculation: (Gross Revenue - Business Expenses) × 92.35% = Taxable Income.
Key Deduction: Half of the SE Tax you pay is deductible from your AGI for income tax purposes.
Strategy: Maximizing legitimate business expenses is the most effective way to reduce net earnings. Retirement plans like a Solo 401(k) or SEP IRA are powerful tools for lowering AGI.
How to Get an Excess Social Security Tax Refund
Cause: Occurs when you have W-2 income from two or more employers, and your total withheld Social Security tax exceeds the annual maximum.
Solution: Claim the excess amount as a "refundable credit" on Form 1040, Schedule 3. This reduces your tax or increases your refund.
Caution: If a single employer mistakenly withholds too much, you cannot claim a credit; you must ask the employer for a refund.
What is Additional Medicare Tax (AMT)?
Who it affects: High-income earners who exceed certain income thresholds based on their filing status.
Tax Rate: An additional 0.9% on income above the threshold (with no employer match).
Thresholds:
- Married Filing Jointly (MFJ): $250,000
- Single, Head of Household (HOH): $200,000
- Married Filing Separately (MFS): $125,000
The Withholding Problem: Employers only start withholding for AMT when an individual's wages exceed $200,000. This can lead to an underpayment for married couples. You must manage your estimated tax liability based on your total household income.