Deductions Small Businesses Miss Most Often
The ordinary, legitimate deductions that go unclaimed because nobody tracked them, grouped by where they hide.
Reviewed by the Fairlight Accounting cross-border tax team — U.S. & Canadian Tax Desks
Missed deductions are usually not exotic. They are ordinary costs that never made it into the books — processing fees netted from deposits, mileage never logged, subscriptions on a personal card — or items that exist only if claimed on the return, such as the startup cost deduction and the qualified business income deduction.
On this page
Which deductions are commonly missed?
| Where it hides | Deduction |
|---|---|
| Netted out of deposits | Merchant and payment processor fees, marketplace fees, chargebacks |
| On a personal card | Software subscriptions, domain and hosting, phone plan share, supplies |
| Never logged | Business mileage, parking and tolls, business share of home internet |
| Not an expense in the books | Depreciation and Section 179 on assets; de minimis purchases expensed |
| Only on the owner's return | Deductible half of self-employment tax; self-employed health insurance; retirement contributions; the 20 percent qualified business income deduction |
| Election or first-year claim | Startup and organizational costs (each up to $5,000 in the first year, reduced dollar for dollar once costs exceed $50,000, with the rest amortized over 180 months); de minimis safe harbor (annual election); home office (regular or simplified method) |
| Written off but not deducted | Bad debts of an accrual-method business; obsolete inventory written down |
| Paid but miscoded | Business credit card interest and annual fees; bank fees; business licenses and local business taxes; state franchise and gross receipts taxes |
| Forgotten entirely | Professional dues and memberships; continuing education; business gifts up to $25; the business share of a home alarm or utilities; shipping and postage |
| Credits, not deductions | Research credit; retirement plan startup credit; work opportunity credit (for hires who began work by December 31, 2025); small employer health credit |
Why do owner-level deductions get missed?
They never appear in the business's profit and loss. The half of self-employment tax, the health insurance deduction, and retirement contributions are claimed on the owner's Form 1040, so a bookkeeper watching the business ledger never sees them, and an owner using software without guidance may skip the screens. The qualified business income deduction is computed on the return from the business's figures and wage data.
What about the ones that need a catch-up?
Depreciation never claimed on an asset can generally be caught up in the current year by filing Form 3115 (once the same wrong treatment appears on two or more consecutive returns) rather than amending past returns. Missed deductions on a filed return can be claimed by amending, generally within three years of filing or two years of paying the tax, whichever is later. Missed elections are harder; the de minimis safe harbor, for example, must be elected on a timely filed original return (including extensions).
What is not a missed deduction?
Personal clothing that could be worn outside work, commuting, fines and penalties, political contributions, the owner's own labor, and personal meals at home. Chasing these creates audit exposure without a deduction.
Frequently asked questions
Are bank and processing fees really deductible?
Yes. Report gross sales and deduct the fees; do not simply report net deposits.
Can I deduct a home office if I also have a shop?
Only if the home office is used regularly and exclusively for the business and is either the principal place of business or a place where you meet clients — or is a separate, unattached structure used in the business.
Do I need receipts for small items?
Keep them; a credit card statement proves payment, not purpose. For travel, meal, gift, and transportation expenses, a receipt is not required for an item under $75 (lodging excepted), but you still need a record of the amount, date, place, and business purpose.
Is the qualified business income deduction automatic?
Software usually computes it, but the inputs — wages, property, business type — must be right, and the deduction is lost if the return omits it.
Official sources
The IRS explains: “To be deductible, a business expense must be both ordinary and necessary. An ordinary expense is one that is common and accepted in your field of business.” — Internal Revenue Service, Publication 334 (2025), Tax Guide for Small Business, https://www.irs.gov/publications/p334
The IRS instructions state: “Include all ordinary and necessary business expenses not deducted elsewhere on Schedule C. List the type and amount of each expense separately in the space provided.” — Internal Revenue Service, Instructions for Schedule C (Form 1040) (2025), https://www.irs.gov/instructions/i1040sc
Next step
Fairlight Accounting handles U.S. domestic, cross-border (U.S.–Canada), and international tax returns, plus bookkeeping, payroll, and CFO advisory. Our U.S. Tax Desk runs a missed-deduction review on every new client's prior-year return. See pricing or book a free fit call.
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