Top Tax Deductions Every Small Business Owner Should Know

The Foundation: What Qualifies as a Business Deduction

The IRS allows deductions for expenses that are "ordinary and necessary" for your business. Ordinary means common and accepted in your trade or business. Necessary means helpful and appropriate (not indispensable). These are the standards your deductions must meet to hold up to scrutiny.

The practical test: Is this expense primarily for your business? If yes, it's likely deductible in full. If it's partly personal and partly business, only the business portion is deductible. When in doubt, document — a legitimate expense with poor documentation is a disallowed deduction in an audit.

The Self-Employment Tax Deduction

Before we get to business expenses, this deduction is unique to the self-employed and often overlooked: you can deduct half of your self-employment tax from your adjusted gross income. This is an above-the-line deduction — it reduces your taxable income even if you take the standard deduction.

Example: If you owe $12,000 in self-employment tax, you can deduct $6,000 from your income. This is calculated on Schedule SE and flows to Schedule 1 of your 1040. Don't miss it.

Home Office Deduction

If you use part of your home exclusively and regularly for business, you can deduct a portion of your housing costs. This is one of the most valuable deductions for self-employed individuals working from home — and one of the most misunderstood.

Two Methods

Simplified Method: $5 per square foot of your home office, up to 300 square feet (maximum deduction: $1,500). Easy to calculate, no depreciation recapture on sale.

Regular Method: Calculate the percentage of your home used for business (office square footage ÷ total home square footage) and apply that percentage to actual home expenses: mortgage interest or rent, utilities, homeowner's insurance, repairs, and depreciation. More complex but often yields a larger deduction.

The "Exclusive Use" Requirement

The space must be used exclusively for business — a desk in your bedroom where you also sleep doesn't qualify. A dedicated room used only for work does. This requirement is strictly enforced and is the most common reason home office deductions fail IRS scrutiny.

Vehicle and Transportation Deductions

Business use of your personal vehicle is deductible. Two methods:

Standard Mileage Rate

In 2026, the IRS standard mileage rate for business is 67 cents per mile (confirm current year rate — it adjusts annually). Track business miles driven and multiply by the rate. This method is simple and includes all vehicle costs (gas, maintenance, insurance, depreciation).

Actual Expense Method

Deduct your actual vehicle costs (gas, insurance, maintenance, repairs, registration, depreciation) multiplied by the percentage of miles driven for business. More complex; may yield a higher deduction for high-cost vehicles with significant business use.

Mileage Tracking is Essential

You must keep a contemporaneous mileage log showing date, destination, business purpose, and miles for each business trip. Reconstructing this after the fact (or estimating) is not acceptable documentation. Apps like MileIQ or Everlance make this easy.

Commuting Is Never Deductible

Driving from home to your regular office is commuting — not a business deduction. Once you're at your office and traveling to a client meeting, that's deductible. Self-employed people with a qualifying home office may have more flexibility since home is their office.

Health Insurance Premiums

Self-employed individuals who pay for their own health, dental, and vision insurance premiums — and are not eligible for coverage through a spouse's employer plan — can deduct 100% of premiums as an above-the-line deduction. This includes premiums paid for yourself, your spouse, dependents, and children under 27.

This is calculated on Schedule 1 (not Schedule C) and reduces your AGI regardless of whether you itemize. It does not reduce self-employment tax — only income tax.

Retirement Plan Contributions

Contributing to a self-employed retirement plan is one of the most powerful tax reduction strategies available. Options:

SEP-IRA (Simplified Employee Pension)

Contribute up to 25% of net self-employment income (approximately 20% of net Schedule C profit), up to $70,000 in 2026. Contributions are fully deductible and easy to set up. Excellent choice for high-income self-employed individuals.

Solo 401(k)

Available to self-employed individuals with no employees (other than a spouse). Contributions can be made both as "employee" (up to $23,500 in 2026, or $31,000 if 50+) and "employer" (up to 25% of compensation). Total contributions up to $70,000. Higher potential contributions than a SEP-IRA for many self-employed individuals.

SIMPLE IRA

Available to self-employed individuals and businesses with up to 100 employees. Employee contribution limit is $16,500 in 2026. Less common for solo operators than SEP-IRA or Solo 401(k).

The Qualified Business Income (QBI) Deduction

The Section 199A QBI deduction allows eligible self-employed individuals and pass-through business owners to deduct up to 20% of qualified business income from their taxable income. This is significant — for a sole proprietor with $100,000 in business profit, this can mean a $20,000 deduction.

Limitations and phase-outs apply:

• For taxpayers above certain income thresholds ($197,300 single / $394,600 joint in 2026), the deduction may be limited for specified service trades or professions (SSTB)
• SSTBs include lawyers, doctors, accountants, financial advisors, and consultants
• Non-SSTBs (contractors, retailers, manufacturers, landlords, etc.) face different W-2 wage and property limitations above the threshold

This deduction is complex enough that consulting a CPA is advisable to maximize it correctly.

Other Commonly Missed Deductions

• Software and subscriptions: Business software, SaaS tools, industry-specific subscriptions, project management tools
• Professional development: Books, courses, webinars, conferences related to your business
• Professional services: Accountant fees, attorney fees, consultant fees
• Bank fees and merchant processing: Business account fees, PayPal/Stripe processing fees, wire transfer fees
• Marketing and advertising: Website costs, paid advertising, printing, business cards, promotional materials
• Business insurance: Liability insurance, errors and omissions, professional indemnity
• Phone and internet: The business-use percentage of your phone and internet bills
• Meals (50% deductible): Business meals with clients or prospects where business is discussed — 50% of the cost with documentation of who, what, and business purpose
• Startup costs: Up to $5,000 of startup costs deductible in the first year, remainder amortized over 15 years
• Section 179 equipment expensing: Deduct the full cost of qualifying equipment and software in the year purchased (up to $1,220,000 in 2026), rather than depreciating over years

Documentation: Your Defense in an Audit

The IRS doesn't simply take your word for deductions. You need documentation:

• Receipts for all expenses (digital copies are acceptable)
• Bank and credit card statements
• Mileage log for vehicle deductions
• Calendar entries for business meetings and meals
• Invoices from contractors and vendors
• Contracts for services

Keep records for at least 3–7 years (the typical audit window is 3 years, but 6 years for substantial underreporting). Use accounting software or a dedicated business bank account to keep business finances separate from personal.

Get Professional Tax and Financial Planning Help

A CPA or fee-only financial advisor specializing in small business can help you maximize deductions, structure your business optimally, and build a tax-efficient financial plan. Find advisors in the National Finance Connect directory.