Quick answer: The deductions business owners miss most often are the ordinary ones that never got recorded: a legitimate home office, business use of a personal vehicle, self-employed health insurance, startup costs, small equipment and software bought on a personal card, and bank and merchant fees. Most missed deductions are a bookkeeping problem, not a tax-law problem, so the fix is capturing expenses as they happen and keeping the support.
After decades of preparing returns, we can say with some confidence that very few owners lose money because they never heard of an obscure tax break. They lose money because a real, deductible expense was paid from the wrong account, recorded in the wrong place, or never recorded at all. Here are the items we see slip through most often, and how to catch them.
Expenses paid personally that belong to the business
The single biggest leak is business spending that runs through personal accounts. A software subscription on your personal credit card, a printer bought at the big-box store on a Saturday, a professional membership renewed from your checking account. None of it shows up in the books unless someone goes looking.
- Review personal card and bank statements at least quarterly for business charges.
- Reimburse yourself from the business with a simple expense report, or record the items as owner contributions.
- Better yet, keep a separate business card and use it for everything business-related.
If your records are a mix of personal and business activity, our article on bookkeeping basics every small business owner should know walks through how to separate them cleanly.
Home office and vehicle use
Both of these are real deductions that owners skip either because they think the rules are too complicated or because they worry about an audit. Neither is a good reason to leave money on the table, as long as you qualify and keep records.
Home office. If part of your home is used regularly and exclusively for business, and it is your principal place of business or where you meet clients, you may qualify. The IRS offers a simplified method based on square footage, or the regular method that allocates actual costs like utilities, insurance, repairs, and depreciation. A spare bedroom that doubles as the guest room does not qualify; a dedicated room in your Syracuse home that holds nothing but your desk and files likely does.
Vehicles. Business miles in a personal vehicle are deductible using either the standard mileage rate, which the IRS sets each year, or actual expenses times your business-use percentage. Commuting from home to a regular workplace does not count, but driving from your office to a client, a supplier, or the bank does. The deduction lives or dies on a mileage log, so keep one, even if it is a simple phone app.
Health insurance and retirement contributions
Self-employed individuals, partners, and more-than-2% S corporation shareholders can often deduct health insurance premiums for themselves and their families. The mechanics differ by entity. For S corporation owners, the premiums generally need to be paid or reimbursed by the company and included in the owner's W-2 wages to be deducted properly. We routinely see this set up wrong, and the fix is easier before year-end than after.
Retirement contributions are the other big one. A SEP-IRA, a SIMPLE IRA, or a solo 401(k) can shelter a meaningful amount of income, and some plans can be funded after year-end. Owners who never set one up are often surprised by how much they could have deducted. Contribution limits are adjusted each year, so check the current figures on the IRS retirement plans page.
Startup costs, small purchases, and depreciation
Startup and organizational costs. If you spent money investigating and launching a business before you opened the doors, a portion of those costs can be deducted in the first year and the rest amortized over 15 years. Many first-year returns skip this entirely because the spending happened before the books were set up.
Small purchases. The IRS de minimis safe harbor lets many businesses expense lower-cost items, such as a laptop, a desk, or a tool, instead of depreciating them, as long as the election is made on a timely filed return and the business has a consistent policy. Without the election, those items may sit on a depreciation schedule for years.
Equipment. Larger purchases can often be written off quickly through Section 179 or bonus depreciation. Our article on depreciation, Section 179, and bonus depreciation explains the choices.
The small, steady expenses that add up
Owners remember the big checks. They forget the dozens of small charges that never had an invoice. Over a year these can easily total a few thousand dollars.
- Bank service charges, merchant processing fees, and payment app fees.
- Software and cloud subscriptions, including the ones billed annually.
- Business portion of your cell phone and internet.
- Professional dues, licenses, and continuing education related to your current business.
- Business insurance, including liability, property, and cyber policies.
- Interest on business loans and business credit cards.
- Business meals with clients or employees, which are generally 50% deductible when documented with who attended and the business purpose. Entertainment, such as tickets to a game, generally is not deductible.
A monthly reconciliation catches most of these automatically, because every fee on the bank statement has to land somewhere.
Frequently asked questions
Can I deduct expenses from a prior year that I forgot to claim?
Often, yes, by filing an amended return, generally within three years of the original filing date. Depreciation errors are handled differently and sometimes require an accounting method change instead of an amendment, so it is worth having someone look at the specifics before you file.
Does claiming a home office increase my audit risk?
A legitimate, well-documented home office deduction is not something to fear. The risk comes from claiming space that is not used exclusively for business. Keep a simple floor plan with measurements and photos of the space, and you will have what you need if anyone asks.
Do I need receipts for every expense?
You need records that show the amount, date, place, and business purpose. Bank and card statements help, but they do not show what was purchased or why. For meals, travel, and vehicle use, the rules are stricter, so keep the receipt and jot a note about the business purpose.
Are New York State deductions the same as federal?
New York starts from federal income for most businesses and individuals, so most business deductions carry through. There are differences in areas like depreciation, where New York does not follow federal bonus depreciation for most taxpayers, so your state and federal numbers can differ.
This article is general information for 2026, not tax or legal advice for your situation. Tax rules and figures change; confirm current amounts with the IRS, New York State, or your accountant before acting.
Related service: Business & Corporate Tax