Earning money outside your regular job comes with tax obligations most people underestimate. Unlike W-2 employment where taxes are withheld automatically, self-employment income arrives gross — you owe both income tax and self-employment tax (Social Security plus Medicare) at filing time. Understanding which deductions you qualify for, how your marginal bracket applies to side income, and when to make quarterly payments prevents costly surprises each April.
Self-Employment Tax: The 15.3% You Might Not Expect
Net SE Income is gross side hustle revenue minus deductible business expenses; the 0.9235 factor accounts for the employer-half deduction; 15.3% covers 12.4% Social Security (up to the wage base) plus 2.9% Medicare. The Social Security portion applies only to the first $184,500 of combined SE and W-2 wage-base earnings in 2026. Regular self-employment tax can apply even when you owe no federal income tax. The $400 Schedule SE threshold applies after multiplying Schedule C profit by 92.35%.
The deductible half-SE-tax adjustment applies to the base Social Security and Medicare portions of self-employment tax. Additional Medicare Tax is not included in this deduction. Actual business cash outlays and full entered health and retirement payments are deducted separately from receipts. Federal tax only; state and local taxes and other household deductions or credits are excluded.
Deductions That Directly Lower Your Tax Bill
Checking an item records a reminder only; it never creates a deduction or confirms eligibility. Other listed expenses belong in the aggregate only once, after you verify their business use and legal limits. Enter zero for an ineligible or unreviewed expense you do not wish to assume. Identify the same amounts, not additional expenses. Included amounts are removed from the aggregate before their allowed deductions are applied. Vehicle actual costs and standard mileage cannot both cover the same use.
For simplified use, enter $5 times eligible square feet, up to 300 square feet; the model also limits it to available business income. For actual use, enter the allowed Form 8829 deduction after its limits; the $1,500 simplified cap does not apply. This calculator does not establish exclusive, regular or principal-place eligibility or calculate carryovers.
Marginal vs. Effective Tax Rate on Side Income
Hypothetical annual net profit before owner adjustments, with entered deduction, payment and cash-basis assumptions held fixed. Federal only; no state increment is modeled. Unsupported QBI points have gaps. The cursor changes this comparison, not your actual inputs.
A tax-profit measure, not spendable cash: receipts less allowed business deductions and modeled additional federal tax. Enter actual cash outlays to include cash costs and owner payments. Actual business cash outlays and full entered health and retirement payments are deducted separately from receipts. Federal tax only; state and local taxes and other household deductions or credits are excluded.
Amounts are saved locally on this browser. Reset clears this calculator’s current and previous draft keys. Shared-link sessions leave the recipient’s local draft unchanged; Reset removes the shared inputs and restores that draft. No client names, trip endpoints or health details are requested.
Quarterly Estimated Taxes: Avoiding Penalties
This reduces the remaining cash-reserve budget only. It is not a calculation of required IRS installments, remaining tax due, safe harbor, penalties or a refund. Four cent-rounded reserves sum exactly to the remaining annual budget; reference dates may not apply to you.
A tax-profit measure, not spendable cash: receipts less allowed business deductions and modeled additional federal tax. Enter actual cash outlays to include cash costs and owner payments. Actual business cash outlays and full entered health and retirement payments are deducted separately from receipts. Federal tax only; state and local taxes and other household deductions or credits are excluded.
Amounts are saved locally on this browser. Reset clears this calculator’s current and previous draft keys. Shared-link sessions leave the recipient’s local draft unchanged; Reset removes the shared inputs and restores that draft. No client names, trip endpoints or health details are requested.