What can I actually write off? The three deductions a checklist cannot size (US, 2026)
Everything below is United States federal tax, for tax year 2026, and it is about a sole proprietor or single-member LLC with no employees. State tax, S corporations, partnerships and anyone running payroll work differently and are not covered here.
What can I write off as a self-employed person?
The list is not the hard part. Mileage, home office, equipment, meals, phone, health insurance, retirement, half your self-employment tax — every checklist has them, and they are all real.
The hard part is how much. On $78,000 of revenue with $6,200 of other expenses, the deductions in this article come to $20,728, leaving $63,348 of net profit. But three of the largest lines are not the amount you paid. They are capped by something the checklist never asked you about.
The home office deduction you can lose for good
The simplified method is $5 a square foot, up to 300 square feet — a maximum of $1,500, and no receipts. That much is well known.
What is not: it cannot create or increase a loss. The deduction is limited to the gross income of the business after your other expenses. And here is the part that costs people money — under the simplified method the unused part does not carry forward. It is gone.
Take a year with $32,000 of revenue and $31,100 of other expenses. The full 300 square feet would give $1,500. The business income allows $900. The remaining $600 is not deferred, not banked, not carried to a better year. It is lost.
The regular method does carry forward, which is the one real argument for using it in a thin year — at the cost of tracking actual household expenses and depreciation. If your business income comfortably exceeds $1,500, the simplified method costs you nothing and takes a minute. If it does not, the choice is worth thinking about before you file, not after.
There is a prior test people fail more often than the cap: the space has to be used regularly AND exclusively for the business. A desk in a room you also live in does not qualify.
Can I deduct my health insurance if my spouse has a plan at work?
No — not for any month that plan was available to you. Not "if you joined it". If you were eligible to take part in a subsidized health plan through an employer, yours or your spouse's, the self-employed health insurance deduction is gone for those months, even if you declined the plan and paid for your own cover instead.
Eligibility is the test, not enrollment. It is the most common reason this deduction is disallowed, and almost no checklist asks the question.
Same revenue, same premiums, same money out of the same pocket: $9,600 of deduction on one side, $0 on the other. The whole difference is one fact about somebody else's job.
Two things worth knowing if the deduction is available to you:
- It is limited to your net profit less the deductible half of your self-employment tax less your retirement contributions. Premiums above that limit are not destroyed — they move to Schedule A as a medical itemized deduction, where a floor applies.
- It covers medical, dental and qualified long-term care premiums, and a spouse's and dependents' as well as your own.
I bought a laptop. Can I just deduct it?
If it cost $2,500 or less, yes. The de minimis safe harbor under Treasury Regulation 1.263(a)-1(f) lets a taxpayer without an applicable financial statement write off the whole cost this year.
At $2,501 it leaves this calculation entirely.
Above the threshold, the item becomes depreciation or a section 179 election — a different form, a different set of limits, and a decision that is not free: the election has to cover every qualifying item you bought that year, not the ones you pick afterwards.
Two details that catch people:
- The test is per item, not per year. One $4,000 laptop is not two $2,000 laptops. Splitting an invoice does not split the item.
- The safe harbor has to be elected for the whole year, on a timely return, and it applies to everything that qualifies.
Do I use one mileage rate for the whole year?
Not in 2026. The IRS set the business standard mileage rate at 72.5 cents for the year in Notice 2026-10 and raised it to 76 cents from 1 July in Announcement 2026-11. Miles before that date and miles from that date are multiplied by different numbers and added.
On 12,000 business miles split 5,000 before 1 July and 7,000 after, the two rates give $8,945. A spreadsheet carrying the first-half rate for the whole year gives $8,700 — $245 left behind, on one ordinary year of driving. Most free mileage sheets still carry a single rate.
Also worth being precise about what counts: a trip between two work locations, to a client, to the bank, to the post office is business mileage. Commuting from home to a regular workplace never is — with one useful consequence, which is that a qualifying home office makes the first trip of the day a business trip rather than a commute.
And the two methods are mutually exclusive for the same car in the same year: the standard mileage rate or actual costs, not both.
Is self-employment tax deductible?
Half of it, and you do not elect it. Schedule SE line 13 comes off your income automatically. On the worked example above, self-employment tax is $8,951 and $4,476 of it is deducted whether or not you ever think about it. The other half is not deductible.
It is on this list only because people ask, and because seeing it as a line makes the health insurance limit above make sense — that half is one of the things subtracted before your premium cap is worked out.
What the amounts look like together
On the $78,000 example:
| Line | Amount | Why that amount |
|---|---|---|
| Vehicle — standard mileage rate | $4,096 | 5,500 miles at two 2026 rates |
| Half of self-employment tax | $4,476 | Schedule SE line 13, automatic |
| Self-employed health insurance | $7,800 | premiums, inside the limit |
| Equipment — de minimis safe harbor | $2,239 | two items at or under $2,500; one above is not included |
| Phone and internet | $792 | 60% business share — the share is what gets challenged |
| Business meals | $725 | half of $1,450; the temporary full deduction expired after 2022 |
| Home office — simplified method | $600 | 120 sq ft at $5 |
| Retirement contribution | $0 | nothing entered — usually the largest one available |
That last line is the most expensive habit on the page. For a profitable sole proprietor a retirement contribution is normally the single largest deduction available, and the ceiling is higher than most people assume — but it is not a flat percentage of profit, because the contribution reduces the earnings it is measured against. The solo 401(k) calculator works out the real one.
Work out your own numbers
The self-employed deduction checklist takes your revenue, mileage split at 1 July, square footage, premiums, equipment costs and phone share, and gives every line an amount, a status and the reason it is that amount — including the three above. It is free, needs no sign-up, runs in your browser and stores nothing. Every figure it prints is checked against an independent model over 159 scenarios before it ships.
It is honest about where it stops, too: no depreciation or section 179, no actual vehicle costs, no regular home office method, no state tax, no employees.
What this does not replace
This is a calculator and an explanation, not tax advice, and it is federal only. Several states treat the home office, section 179 and health insurance differently, and a state can quietly reverse the conclusion of any comparison on this page. If your year has employees, a partnership, an S corporation, rental property or a business loss you want to carry, the questions get bigger than a checklist — and that is exactly when it is worth paying someone.
