Every year we review returns prepared elsewhere and find deductions the owner qualified for but never claimed. None of these are aggressive or gray-area — they're ordinary, legitimate deductions that get missed because nobody asked the right question. Here are the ones we catch most often.
1. The home office deduction
If you use part of your home regularly and exclusively for business, you can deduct a portion of your rent or mortgage interest, utilities, insurance, and repairs. The simplified method gives you a flat rate per square foot; the actual-expense method often deducts more. Working from your kitchen table doesn't count — 'exclusively' is the key word.
2. Business use of your car
You can deduct either the standard mileage rate for every business mile or the actual costs of operating the vehicle for business. Most people forget to track mileage all year, then lose the deduction. Use an app that logs trips automatically — those miles add up fast.
3. The Qualified Business Income (QBI) deduction
Pass-through owners can often deduct up to 20% of qualified business income — one of the most valuable deductions available to small businesses, and one that's easy to under-optimize. Phase-outs and limits apply above certain income thresholds, which is exactly where planning pays off.
4. Self-employed health insurance
If you're self-employed and pay for your own health, dental, or qualifying long-term care insurance, you can generally deduct those premiums — for yourself, your spouse, and dependents — even if you don't itemize.
5. Retirement contributions
A SEP-IRA, SIMPLE IRA, or Solo 401(k) lets you shelter a significant chunk of income from tax while building your own retirement. This is one of the biggest levers a profitable small business has, and it's routinely underused.
Almost every missed deduction traces back to one of two things: no records kept during the year, or nobody asked whether it applied. A monthly bookkeeping habit and a year-end review fix both.
6–12. The ones that add up quietly
- Phone and internet — the business-use percentage is deductible, not just a separate business line.
- Startup costs — you can deduct a portion of what you spent getting the business off the ground, and amortize the rest.
- Professional development — courses, certifications, books, and industry subscriptions tied to your work.
- Business meals — generally 50% deductible when there's a clear business purpose; keep the who/why with the receipt.
- Bank and merchant fees — monthly account fees and payment-processing fees (Stripe, Square, PayPal) are fully deductible.
- Software and subscriptions — the tools you run your business on, from accounting software to design apps.
- Professional fees — what you pay your accountant, attorney, and other advisors is itself deductible.
How to actually capture these
- 1Run business expenses through a dedicated business account and card — no commingling.
- 2Keep records as you go, not in April. A bookkeeping habit turns tax season into a non-event.
- 3Track mileage and home-office use with an app so the numbers are defensible.
- 4Have an accountant review your return before filing — a second set of eyes catches what software prompts miss.
Tax software asks you what you know to enter. An accountant asks what you didn't know to look for. That gap is where the missed deductions live.
A quick note: deductions are powerful but rule-bound — 'exclusively,' 'ordinary and necessary,' and income thresholds all matter. When in doubt, document it and ask. If you'd like a second look at last year's return to see what was left on the table, we offer a free review. This article is general information, not tax advice for your specific situation.