Money you earn from self-employed professional work — consulting, medicine, law, design, engineering, freelance code — is taxed twice over: once at ordinary income tax rates and again at a flat 15.3% self-employment tax. The professional income tax rules and deductions that apply to you all flow from that structure. You report the work on Schedule C of Form 1040, calculate self-employment tax on Schedule SE, and use a set of specific write-offs (business expenses, home office, health insurance, retirement contributions, and the 20% qualified business income deduction) to bring the total down.
How Professional Income Is Taxed
The IRS does not run a separate category for “professional income.” Whether you practice medicine, run an architecture firm, or freelance as a developer, if you operate as a sole proprietor the treatment is the same: gross receipts and deductible expenses go on Schedule C (Form 1040), and the net profit flows to your 1040 as ordinary income.1Internal Revenue Service. Instructions for Schedule C (Form 1040)
The IRS does care whether your activity is a business or a hobby, because only a business gets the full deduction set below. The agency weighs whether you keep accurate records, how much time and effort you put in, whether the income supports your livelihood, and whether you’ve adjusted your methods to improve profitability.2Internal Revenue Service. Here’s How to Tell the Difference Between a Hobby and a Business for Tax Purposes There’s a working presumption: profit in three of the last five years, and the IRS treats the activity as a business.3Internal Revenue Service. Business or Hobby? Answer Has Implications for Deductions Falling short doesn’t automatically make you a hobby, but it invites scrutiny.
The Self-Employment Tax Layer
This is the layer that surprises people leaving a salaried job. A W-2 employee splits Social Security and Medicare taxes with the employer; a self-employed professional pays both halves. The combined rate is 15.3%: 12.4% for Social Security and 2.9% for Medicare.4Office of the Law Revision Counsel. 26 USC 1401 – Rate of Tax
The tax applies to 92.35% of your net profit, not the whole figure, which mirrors the tax break employers get on their share.5Internal Revenue Service. Topic No. 554, Self-Employment Tax The 12.4% Social Security portion stops at the wage base, $184,500 for 2026.6Social Security Administration. Contribution and Benefit Base The 2.9% Medicare portion has no cap.
High earners owe an additional 0.9% Medicare surtax on self-employment income above $200,000 (single) or $250,000 (married filing jointly).7Internal Revenue Service. Topic No. 560, Additional Medicare Tax One partial offset built into the code: you can deduct half of your self-employment tax when calculating adjusted gross income. That doesn’t reduce the self-employment tax itself, but it does shrink the income subject to your regular rate.
Quarterly Estimated Payments
Nobody withholds tax from your client payments, so you send it in yourself, four times a year. For the 2026 tax year the deadlines fall on April 15, June 15, and September 15 of 2026, plus January 15, 2027. Underpay any installment and interest-like penalties accrue on the shortfall.8Internal Revenue Service. 2026 Form 1040-ES
You need to pay estimates if you expect to owe at least $1,000 after withholding and refundable credits. To avoid a penalty, your payments must cover the smaller of 90% of your current-year tax or 100% of last year’s tax. If your 2025 adjusted gross income was over $150,000 ($75,000 if married filing separately), the prior-year safe harbor rises to 110%.8Internal Revenue Service. 2026 Form 1040-ES For professionals with lumpy income, the prior-year number is the easier target because you already know it.
Deductions That Reduce Your Tax
The other side of self-employment taxation is a broad deduction set. An expense qualifies if it’s ordinary (common and accepted in your field) and necessary (helpful and appropriate for your work). “Necessary” doesn’t mean indispensable.9Internal Revenue Service. Ordinary and Necessary
Typical deductible items include:
- Office rent and utilities, including electricity and internet.
- Wages and contractor payments, plus the payroll taxes that ride along with them.
- Books, courses, conferences, and continuing education tied to your field.
- Business travel: transportation, lodging, and meals at 50%.
- Depreciation on equipment, computers, and furniture.
- Business mileage at 72.5 cents per mile for 2026.10Internal Revenue Service. Standard Mileage Rates Updated for 2026
- Professional license renewals, bar dues, and board certification fees, typically $50 to $325 a year depending on the profession and state.
Home Office
Use part of your home exclusively and regularly as your principal place of business, and you can deduct a share of your housing costs. The word doing the work is “exclusively.” A spare bedroom that also hosts guests does not qualify.11Internal Revenue Service. How Small Business Owners Can Deduct Their Home Office From Their Taxes
The simplified method gives you $5 per square foot, up to 300 square feet, capped at $1,500. The regular method takes the business-use percentage of your home and applies it to rent or mortgage interest, utilities, insurance, and repairs. It requires more recordkeeping but often produces a larger deduction, particularly in high-cost areas.
Health Insurance Premiums
Self-employed professionals can deduct 100% of health, dental, and qualifying long-term care insurance premiums paid for themselves, a spouse, and dependents. The deduction is an adjustment to gross income on Schedule 1, so you get it whether you take the standard deduction or itemize. You cannot claim it for any month you were eligible to join a subsidized plan through a spouse’s employer or another job of your own.
The 20% Qualified Business Income Deduction
Section 199A lets eligible self-employed individuals deduct up to 20% of their qualified business income from taxable income. On $100,000 of profit that’s a potential $20,000 subtraction before any other deduction runs. The One, Big, Beautiful Bill Act made the deduction permanent and set a $400 minimum for owners with at least $1,000 in qualified business income.
Your profession matters here. The statute labels certain fields as “specified service trades or businesses,” which sweeps in law, medicine, accounting, consulting, and financial services. Below defined income thresholds, the profession label doesn’t matter and the full 20% is available. Above the thresholds, the deduction for specified service professionals phases out and eventually disappears. Non-service work such as engineering or architecture runs into different limits at the same thresholds and generally keeps more of the deduction at higher incomes.
Retirement Contributions as a Tax Shelter
Contributions to a self-employed retirement plan are deductible and grow tax-deferred, which makes them one of the largest levers you have.
- SEP-IRA: up to 25% of net self-employment earnings, capped at $72,000 for 2026. Almost no paperwork.12Internal Revenue Service. SEP Contribution Limits
- Solo 401(k): up to $24,500 as employee deferral plus an employer contribution of up to 25% of net earnings, combined ceiling $72,000. Ages 60 to 63 can push the total to $83,250 with catch-ups.13Internal Revenue Service. Retirement Topics – 401(k) and Profit-Sharing Plan Contribution Limits
- SIMPLE IRA: up to $17,000 in salary reduction for 2026, plus a $4,000 catch-up at age 50 or $5,250 at ages 60 to 63.14Internal Revenue Service. Publication 560, Retirement Plans for Small Business
The Solo 401(k) tends to shelter the most income for high earners because the employee deferral piece kicks in before the percentage-of-profit calculation. A SEP-IRA is hard to beat on simplicity if you don’t need the maximum shelter.
Recordkeeping and Filing
Good records are your only defense in an audit. Keep receipts, bank statements, invoices, and mileage logs for every income item and deduction you claim.15Internal Revenue Service. Topic No. 305, Recordkeeping The standard retention period is three years from the filing date; if you understated gross income by more than 25%, the IRS has six years to assess additional tax, so six years is the safer default.16Internal Revenue Service. How Long Should I Keep Records Digital records are fine: receipt photos, cloud accounting software, exported statements. What matters is capturing expenses as they happen rather than reconstructing a year in April. Professionals who lose deductions in audits usually lose them for lack of proof, not because the expense was fake.
All of this comes together on a handful of forms. Schedule C carries your gross receipts, expenses, and net profit. Schedule SE computes the self-employment tax. Schedule 1 holds the half-of-self-employment-tax deduction, the health insurance deduction, and your retirement plan contributions as adjustments to income. The qualified business income deduction is calculated on its own form and subtracted from taxable income on the 1040.
One threshold worth knowing on the income side: clients must issue a Form 1099-NEC when they pay you $2,000 or more during the year. That figure rose from $600 for payments made on or after January 1, 2026, and will index for inflation starting in 2027.17Internal Revenue Service. Publication 1099, General Instructions for Certain Information Returns Income below the reporting threshold is still taxable; the threshold only governs when your client must file the form.