5 Tax Deductions Small Business Owners Miss Every Year

After preparing hundreds of small business returns every year, I've noticed a pattern: the same deductions get missed over and over. These aren't obscure loopholes. They're legitimate, well-established deductions that the tax code specifically provides for business owners. If you're leaving any of these on the table, you're paying more tax than you need to.

1. Home Office Deduction

This is the most commonly missed deduction I see. If you use a dedicated space in your home regularly and exclusively for business, you qualify for the home office deduction. There are two methods: the simplified method ($5 per square foot, up to 300 square feet, for a maximum $1,500 deduction) and the regular method, which is based on the percentage of your home used for business applied to actual expenses like mortgage interest, property taxes, utilities, insurance, and repairs.

Many business owners skip this deduction because they've heard it triggers audits. That's a myth from decades ago. The IRS has explicitly created the simplified method to make this deduction easier to claim. If you qualify, take it.

2. Vehicle Expenses

If you use your personal vehicle for business, such as driving to client sites, picking up supplies, going to the bank, or meeting with vendors, those miles are deductible. The standard mileage rate for 2026 is set by the IRS annually and typically amounts to a significant deduction for business owners who drive regularly. The key requirement is a contemporaneous mileage log: date, destination, business purpose, and miles driven. Many business owners drive thousands of business miles per year but fail to track them, losing out on a deduction worth $3,000–$6,000 or more.

3. Retirement Contributions

Self-employed individuals have access to powerful retirement savings vehicles that double as tax deductions. A SEP-IRA allows contributions up to 25% of net self-employment income. A Solo 401(k) can allow even higher contributions with both employee deferrals and employer contributions. These contributions reduce your taxable income dollar-for-dollar, and you're building retirement savings at the same time. I regularly see business owners who don't realize they can contribute $20,000, $40,000, or even $60,000+ to retirement accounts and deduct every penny of it.

4. Self-Employed Health Insurance

If you're self-employed and pay for your own health insurance (medical, dental, and qualifying long-term care premiums), you can deduct the full cost as an adjustment to income, not as an itemized deduction. This is an above-the-line deduction, meaning you get it even if you take the standard deduction. For a family paying $15,000–$25,000 per year in premiums, this is a substantial tax savings that many self-employed individuals either don't know about or forget to claim.

5. Professional Development & Education

Courses, conferences, books, certifications, coaching programs, industry memberships, and subscriptions that maintain or improve your skills in your current business are fully deductible. This includes online courses, webinars, and even travel to attend industry conferences (including airfare, hotel, and meals). The key is that the education must relate to your current business. You can't deduct law school if you're a plumber, but you can deduct a plumbing certification course, a business management seminar, or a marketing workshop.