A deduction is a dollar of business expense that comes off your income before tax is calculated. For a freelancer in a 22% federal bracket plus 15.3% SE tax plus 5% state tax, every $100 of legitimate deductions saves roughly $35-42 in combined tax. Track them carefully and the cumulative effect on a year's tax bill is usually four or five figures. Skip the tracking and you simply hand the IRS money you did not have to.
The catch is that "legitimate" is doing a lot of work in that sentence. The IRS standard is "ordinary and necessary" for your trade or business — broad in theory, but with specific rules for the high-value categories.
The big categories for freelancers
**Home office.** The simplified method gives you $5 per square foot of dedicated home-office space, capped at 300 sq ft ($1,500/year). The actual-expense method lets you deduct a percentage of rent, utilities, insurance, and depreciation based on the office's share of your home — usually larger but more record-keeping. The space must be used regularly and exclusively for business.
**Business mileage.** The IRS publishes a standard mileage rate annually (currently in the high 60-cent range per mile). Track every business trip with date, destination, purpose, and miles. Apps like MileIQ make this painless; a notebook works too.
**Health insurance.** Self-employed people can deduct 100% of health, dental, and qualified long-term care premiums for themselves, their spouse, and dependents — as an above-the-line adjustment, meaning it reduces both income tax and AGI without needing to itemize. You cannot be eligible for a subsidized employer plan to qualify.
**Retirement contributions.** A SEP-IRA lets you contribute up to 25% of net self-employment income (with a high annual cap). A Solo 401(k) usually allows even more for higher earners by combining employee deferrals with employer profit-sharing. Both reduce taxable income today.
**Half of SE tax.** Always above-the-line, automatic if you file Schedule SE. Worth calculating once you see how much SE tax you actually owe — use the Self-Employment Tax Calculator.
**The 20% QBI deduction.** Most freelance income qualifies for the Qualified Business Income deduction — a 20% reduction in taxable business income, subject to phase-outs at higher incomes and limits for "specified service trades." This is the single most valuable break the 2017 Tax Cuts and Jobs Act gave self-employed workers.
Smaller but worth tracking
Software and SaaS subscriptions, professional development (courses, books, conferences), business meals (50% deductible with proper documentation), advertising and marketing, contract labor you pay out, business banking fees, payment processor fees (Stripe, PayPal, etc.), and a portion of your phone and internet bills based on business use.
How deductions show up in tax math
Every FreelanceMath calculator that estimates total tax accepts a deduction input. The 1099 Tax Calculator subtracts your deductions from gross income before calculating SE tax, federal tax, and state tax — so you can see the cumulative effect across all three layers. Run the same scenario with $0 deductions and then with your actual tracked total to see the real-dollar impact.
The habit that matters most
Track expenses as they happen, not in a panic at year-end. A simple monthly review — 15 minutes with your bank and credit card statements, sorting business charges into categories — catches the dozens of small deductions that otherwise get lost.