Self-Employment Tax Explained for 2026

Profit is the starting point

Self-employment tax generally starts with net profit, not gross customer payments. Ordinary and necessary business expenses are normally considered before Schedule SE. The calculator assumes the entered profit has already reached that stage; it does not decide whether an expense is deductible.

Schedule SE generally multiplies net profit by 92.35% to estimate net earnings subject to the Social Security and Medicare calculation. That factor reflects the employer-equivalent portion built into the statutory method.

The regular rate has two parts

The regular self-employment tax rate combines 12.4% for Social Security and 2.9% for Medicare. The 2026 Social Security wage base is $184,500. Medicare has no wage-base cap.

Employee wages matter because the Social Security base is shared. Covered W-2 wages generally consume the base before self-employment earnings. A person with $184,500 or more of covered employee wages may have no remaining Social Security portion on self-employment earnings, but Medicare tax can still apply.

Use the self-employment tax calculator to coordinate employee wages and business profit.

Additional Medicare tax is separate

Additional Medicare tax is 0.9% above statutory combined-income thresholds: $250,000 for married filing jointly, $125,000 for married filing separately, and $200,000 for other filing statuses. It has no employer match.

The threshold calculation can combine Medicare wages and self-employment earnings. Employer withholding rules may begin at $200,000 of wages regardless of filing status, so the amount withheld from payroll and final liability can differ for married taxpayers.

Why one-half is shown as a deduction

When calculating adjusted gross income, a taxpayer may generally deduct one-half of the regular self-employment tax. That adjustment does not refund half the tax and does not reduce the Schedule SE total. It can reduce income subjected to regular federal income-tax brackets.

Additional Medicare tax is not included in the calculator’s deductible-half figure. The estimate displays it separately to avoid overstating the adjustment.

Self-employment tax is not the entire quarterly payment

Quarterly estimated payments may need to cover regular income tax, self-employment tax, and other taxes after accounting for withholding and credits. A contractor who reserves only 15.3% can still be short because regular income tax is separate. Someone with substantial W-2 withholding may need less additional payment than the same business profit suggests in isolation.

Estimate regular tax with the federal income tax calculator, then consult Publication 505 for timing and safe-harbor rules. Multiple businesses, farm income, clergy rules, optional methods, partnerships, S corporations, and state obligations need more complete treatment than this educational model.