17 Small-Business Tax Deductions Owners Miss Every Year
Most owners don't overpay their taxes because they're careless — they overpay because they don't know a deduction exists, or they didn't keep the record that supports it. Here are 17 that quietly slip through the cracks.
Direct answer: The deductions small-business owners miss most are the ones that require a little tracking — home office, mileage, self-employed health insurance, retirement contributions, and the QBI deduction — plus a long tail of ordinary expenses like bank fees, software, and startup costs. Any expense that's ordinary and necessary for your business is generally fair game.
The rule behind every deduction
Before the list, the standard the IRS actually applies: a business expense is deductible if it's ordinary (common and accepted in your field) and necessary (helpful and appropriate for your business). Keep the receipt, tie it to a business purpose, and most legitimate costs qualify.
17 deductions owners leave on the table
1. The home-office deduction
If you use part of your home regularly and exclusively for business, you can deduct it — either the simplified $5/sq. ft. method (up to 300 sq. ft. = $1,500 max) or the regular method based on actual home costs. Details in our home-office deduction guide.
2. Business mileage
The 2026 standard mileage rate is 72.5 cents per mile. Even modest business driving adds up — 6,000 miles is a $4,350 deduction. You need a log; a phone app makes it painless.
3. Self-employed health insurance
If you're self-employed and not eligible for an employer plan, you can generally deduct 100% of premiums for yourself, your spouse, and dependents — as an above-the-line adjustment, not just an itemized deduction.
4. Retirement plan contributions
One of the biggest missed opportunities. For 2026 you can contribute to a SEP-IRA (up to 25% of compensation, max $72,000), a Solo 401(k) (employee deferral up to $24,500, plus employer contributions), or a SIMPLE IRA — and deduct it.
5. The QBI deduction
The 20% qualified business income deduction (Section 199A) was made permanent by the One Big Beautiful Bill Act starting in 2026, with phase-in thresholds of $201,750 (single) and $403,500 (married filing jointly). New for 2026: a minimum $400 deduction if you have at least $1,000 of QBI and materially participate.
6. Section 179 & bonus depreciation
Buy equipment, machinery, computers, or qualifying vehicles and you can expense them immediately. Section 179 allows up to $2,560,000 in 2026 (phase-out starts at $4,090,000), and 100% bonus depreciation is now permanent for assets acquired after January 19, 2025.
7. Startup costs
First year in business? You can deduct up to $5,000 of startup costs and $5,000 of organizational costs, with the rest amortized. Owners routinely forget the money they spent before opening.
8. Software and subscriptions
Accounting software, design tools, project management, cloud storage, industry subscriptions — all deductible, and easy to overlook because they're small recurring charges.
9. Bank and merchant fees
Business bank fees, credit card processing fees (Stripe, Square, PayPal), and payroll processing fees are fully deductible.
10. Business use of your cell phone and internet
The business-use percentage of your phone and home internet is deductible. If your plan is $100/month and it's 60% business, that's a $720 annual deduction.
11. Professional development
Courses, certifications, books, industry conferences, and trade publications that maintain or improve skills for your current business.
12. Professional and legal fees
What you pay your CPA, attorney, bookkeeper, and consultants is deductible — including the fee for preparing the business portion of your return.
13. Business meals
Generally 50% deductible when there's a business purpose and you're present with a client, prospect, or business associate. Keep the receipt and note who and why.
14. Continuing insurance premiums
Liability, professional/malpractice, business property, and business-interruption insurance are all deductible business expenses.
15. Interest on business loans and cards
Interest on loans and credit cards used for business purposes is deductible — a reason to keep business and personal borrowing separate.
16. Bad debts
If you use accrual accounting and a customer never pays an invoice you already reported as income, you may be able to deduct it as a bad debt.
17. Health Savings Account (HSA) contributions
If you have a qualifying high-deductible health plan, you can deduct HSA contributions up to $4,400 (self-only) or $8,750 (family) for 2026 — triple tax advantage and often forgotten by owners.
A quick reference table
| Deduction | 2026 figure to know |
|---|---|
| Home office (simplified) | $5/sq. ft., max 300 sq. ft. ($1,500) |
| Standard mileage | 72.5 cents/mile |
| Section 179 | Up to $2,560,000 |
| SEP-IRA | Up to 25% of comp / $72,000 |
| Solo 401(k) employee deferral | $24,500 |
| HSA | $4,400 self / $8,750 family |
| QBI deduction | 20% (permanent), $400 minimum |
Why these get missed — and how to stop it
Nearly every deduction on this list dies for the same reason: no record at the moment of the expense. You can't reconstruct a mileage log or a home-office measurement in April with any confidence. The fix is a simple, consistent bookkeeping habit — categorize expenses monthly, log miles as you drive, and keep receipts digitally.
A good CPA doesn't just find these at filing time; they set up your year so the deductions are captured automatically. If you suspect you've been leaving money on the table, our tax planning service reviews your prior returns and your current setup to catch what's being missed. Book a consultation and we'll take a look.
This is general information, not tax advice. Deductibility depends on your facts — confirm specifics with a CPA before claiming.
Frequently asked questions
What business expenses are tax deductible? Any expense that is ordinary and necessary for your trade or business is generally deductible — including supplies, software, advertising, professional fees, business travel, a portion of your vehicle and home costs, and employee/contractor pay.
What is the most overlooked small-business tax deduction? The home-office deduction, business mileage, self-employed health insurance, and retirement plan contributions are the deductions owners most often miss — each can be worth thousands of dollars.
Can I deduct my car for business? Yes, either using the 2026 standard mileage rate of 72.5 cents per mile or the actual-expense method. You need a mileage log to substantiate business use either way.
What is the Section 179 deduction for 2026? Section 179 lets you immediately expense up to $2,560,000 of qualifying equipment placed in service in 2026, with a phase-out beginning at $4,090,000. 100% bonus depreciation is also available and now permanent.
Is the QBI deduction still available in 2026? Yes. The 20% qualified business income (QBI) deduction was made permanent by the One Big Beautiful Bill Act starting in 2026, and now includes a minimum $400 deduction for active businesses with at least $1,000 of QBI.