AfterTaxLabSelf-employment tax: what the payroll numbers do and do not cover
Payroll taxes fund Social Security and Medicare programs through mandatory withholdings on earned income. These contributions appear as standard deductions on paystubs for workers classified as employees. Employers are legally required to withhold these specific percentages from every paycheck to ensure that federal obligations are met throughout the fiscal year.
The tax system divides these contributions into two equal portions between the worker and the employer. While employees only see their portion deducted directly from their gross pay, the total tax liability remains consistent. Understanding this split clarifies why the take-home pay shown on this calculator reflects only the portion legally attributed to the worker.
Employee-side payroll tax as modelled here
The AfterTaxLab engine charges the employee half of Social Security and Medicare only. No employer share and no self-employment rate are modelled.
| Gross earnings | Social Security | Medicare | Payroll tax |
|---|---|---|---|
| $50,000 | $3,100 | $725 | $3,825 |
| $100,000 | $6,200 | $1,450 | $7,650 |
| $184,500 | $11,439 | $2,675 | $14,114 |
The half the engine models
The engine charges $7,650 of payroll tax on a $100,000 salary — the employee half only. By focusing exclusively on this segment, the calculator displays the standard deduction that a traditional employee expects to see on their paystub. This reflects the reality of a shared tax burden where the employer manages the matching half of the total social insurance contribution.
Why a freelancer’s bill is higher
It has no self-employment rate, so a freelancer’s payroll bill is larger than any figure this site prints. Self-employed individuals are responsible for both the employer and employee portions of these taxes, effectively doubling the total cost compared to the figures displayed here. Because the engine is designed for standard payroll scenarios, it does not account for the higher tax impact experienced by independent contractors.
Where the ceiling still applies
The Social Security part is capped at a wage base of $184,500, which applies to self-employed earnings as well. Once annual earnings exceed this threshold, the Social Security portion of the tax obligation ceases for the remainder of the calendar year. Income tax is a separate line: federal tax on $100,000 is $13,170 before any self-employment adjustment.
Self-employment tax: common questions
Why is my total tax bill higher than what the calculator shows?
The calculator only displays the employee-side payroll tax. Freelancers must pay both the employee and employer portions of these taxes. Because the calculator does not have a self-employment rate, it cannot account for the full tax burden that independent contractors are required to pay to the government.
Does the wage base limit still apply if I am self-employed?
Yes, the Social Security portion is capped at a wage base of $184,500. This ceiling applies to all earned income regardless of your employment status. Once your total earnings for the year surpass this specific amount, you no longer owe the Social Security portion of the payroll tax on additional income.
How does the calculator handle federal income tax?
Federal income tax is calculated as a separate line from payroll taxes. For instance, the federal tax on $100,000 is $13,170 before any self-employment adjustment. This figure is distinct from the payroll taxes used to fund Social Security and Medicare, which are subject to different rules and caps.
Are there tax differences for higher salaries?
Higher salaries reach the Social Security wage base of $184,500, where the tax calculation changes. Once you cross this threshold, the payroll tax deduction decreases because the Social Security portion is no longer withheld. The calculator displays the resulting tax amounts for different salary levels to help illustrate these changing payroll obligations.
Figures calculated with the AfterTaxLab 2026 engine: federal brackets and standard deduction ($16,100 single), Social Security wage base $184,500, published 2026 state rates. Estimates for planning only — not tax advice. Last verified 21 Sep 2026 · methodology.