Side Hustle Taxes Explained: How to Calculate and Pay Quarterly Estimated Taxes

When you earn side hustle income, no employer withholds taxes from your paycheck. That means the IRS expects you to pay taxes as you earn, four times per year. Missing quarterly estimated tax payments triggers an underpayment penalty even if you pay in full at tax time. Understanding the calculation prevents a painful surprise every April.

Who owes quarterly estimated taxes

You owe quarterly estimated taxes if you expect to owe at least $1,000 in federal tax from self-employment income after subtracting withholding and credits. If your side hustle earns more than $400 in net profit in a year, you will file Schedule SE and almost certainly owe quarterly payments the following year.

The self-employment tax calculation

Self-employment tax is 15.3% of net self-employment income up to the Social Security wage base ($176,100 in 2026). This covers both the employer and employee share of Social Security and Medicare. You can deduct half of SE tax from your gross income on your 1040, which softens the blow.

Calculating your quarterly payment

The safe harbor rule: pay at least 100% of last year's total tax liability divided by four, or 110% if your prior year AGI exceeded $150,000. Alternatively, calculate 90% of your current year expected tax and pay one quarter of that amount each quarter. Most side hustlers find the safe harbor method simpler and safer.

What counts as a deductible business expense

Every dollar of legitimate business expense reduces your net profit, which reduces both income tax and self-employment tax. Common deductible expenses include home office (dedicated space), business mileage (67 cents per mile in 2026), equipment and software, professional development, and marketing costs. Keep receipts and track expenses monthly, not annually.