Tax software is good at doing the math on deductions you tell it about. It's much worse at telling you which deductions exist in the first place if you don't know to look for them. Here are the ones that get missed most often.
State sales tax instead of state income tax
If you live in a state with no income tax, or you made a large purchase (a car, a boat, major home renovation materials) during the year, you can deduct state and local sales tax instead of income tax if it works out to more — but only if you itemize, and it still falls under the same SALT cap covered in our 2026 tax changes guide.
Job-hunting and moving costs (in specific circumstances)
Most job-search and moving expense deductions were eliminated for regular employees under prior tax law changes, but active-duty military members relocating due to a permanent change of station can still deduct unreimbursed moving expenses. If that describes your situation, don't assume the general rule applies to you.
HSA contributions made outside payroll
If you contributed to a Health Savings Account with your own after-tax money — not through payroll deduction — that contribution is still deductible, but tax software only catches it if you manually enter it. Payroll HSA contributions are already pre-tax and don't need a separate deduction; direct contributions do.
Easy to miss: student loan interest is deductible up to $2,500 per year even if you take the standard deduction — it's an above-the-line adjustment, not an itemized deduction. Income phase-outs apply, but many filers who assume "I'm not itemizing so this doesn't apply to me" skip a deduction they're actually eligible for.
State tax refund from last year (as income, not a deduction — but easy to get wrong either way)
If you itemized last year and deducted state income tax, and then received a state refund this year, that refund can be taxable income this year — but only up to the amount that actually reduced your federal tax last year. Software handles this correctly if you answer the prior-year itemization questions accurately, but skipping that section is a common source of errors in either direction.
Home office deduction, for the self-employed specifically
W-2 employees generally cannot claim a home office deduction under current law, even if they work from home full-time. Self-employed filers and freelancers can, using either the simplified method ($5 per square foot, up to 300 square feet) or the actual-expense method, which requires more documentation but can produce a larger deduction for a dedicated, regularly-used space.
Charitable contributions you made but didn't get a receipt for
Cash placed in a collection plate, small non-cash donations, and mileage driven for volunteer work (14 cents per mile, a flat statutory rate not adjusted for inflation) are all deductible if you itemize, even without a formal receipt for amounts under $250 — though keeping some record is still wise if you're ever asked to substantiate it.
This is general information, not personalized tax advice. A CPA or enrolled agent can confirm which of these actually apply to your specific return.