How a deduction actually reduces your tax bill
A business deduction reduces your net self-employment profit — the number both your income tax and your self-employment tax are calculated from. That second part matters more for the self-employed than it does for an employee: because self-employment tax applies to net profit, a deduction that lowers profit reduces both taxes at once, not just income tax.
The IRS standard for what qualifies is that an expense must be "ordinary and necessary" for your business — ordinary meaning common and accepted in your field, necessary meaning helpful and appropriate for the business, not indispensable in the strictest sense. Purely personal expenses don't qualify just because they happened during a workday.
Tip Since deductions lower your net profit, update your inputs in the Quarterly Tax Estimator whenever your estimate of this year's deductible expenses changes materially — it directly changes your estimated quarterly payment.
Deductions freelancers claim most often
These show up across most self-employed tax returns, though eligibility for each depends on your specific facts:
| Deduction | What it covers | Key requirement |
|---|---|---|
| Home office | A portion of rent or mortgage interest, utilities, and insurance | Space must be used regularly and exclusively for business |
| Health insurance premiums | Self-employed health insurance premium deduction | Not eligible if you or your spouse can access an employer-subsidized plan |
| Retirement contributions | SEP-IRA, Solo 401(k), or SIMPLE IRA contributions | See our Retirement Accounts guide for account-specific rules |
| Equipment & software | Computers, cameras, tools, and subscriptions used for the business | Mixed personal and business use requires an allocated percentage |
| Vehicle & mileage | Business use of a personal vehicle | Requires a mileage log or actual-expense records; regular commuting doesn't count |
| Self-employment tax deduction | Half of your self-employment tax | Applied automatically as an income adjustment, not itemized separately |
Key Takeaway A deduction lowers your taxable profit, not your tax bill directly. A $1,000 deduction at roughly a 30% combined tax rate saves about $300, not $1,000 — deductions are genuinely valuable, but they're not free money.
Step-by-step: the home office deduction
This is one of the most commonly claimed — and most commonly misunderstood — deductions, so it's worth walking through on its own:
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Confirm regular and exclusive use.
The space must be used only for business, on a regular basis. A kitchen table used for both dinner and invoicing generally doesn't qualify — a dedicated desk or room typically does.
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Choose a calculation method.
The simplified method applies a flat rate per square foot, up to a maximum, with minimal recordkeeping. The actual expense method applies the office's percentage of your home's total square footage to your real housing costs, including depreciation.
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Compare which method yields a larger deduction.
The simplified method is easier to calculate; the actual expense method sometimes produces a larger deduction, particularly in a home with higher housing costs. It's worth estimating both.
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Keep records regardless of the method chosen.
Square footage measurements, a simple floor plan, and dated photos are good practice even under the simplified method, in case the deduction is ever questioned later.
Recordkeeping: what determines audit risk
A legitimate deduction with poor documentation and a legitimate deduction with good documentation are treated very differently if a return is ever questioned — the expense being real isn't enough on its own. Useful records generally include the original receipt or invoice, the payment record (bank or card statement), and a brief dated note about the business purpose, especially for expenses that could otherwise look personal.
For vehicle use, that means a mileage log kept as trips happen, not reconstructed months later from memory. For equipment or software with mixed personal and business use, that means a documented, reasonable basis for the business-use percentage claimed. General IRS guidance recommends keeping tax records for at least three years from when a return was filed, longer in specific situations — confirm the current guidance for your circumstances.
Common mistakes
- Deducting an expense that's common in general but not clearly connected to earning business income — ordinary alone isn't the full standard.
- Claiming 100% business use of a vehicle or device that's clearly also used personally, without an honest allocated percentage.
- Claiming a home office space that isn't used exclusively for business, or skipping the square-footage measurement entirely.
- Waiting until tax season to reconstruct a mileage log or expense records instead of tracking them as the year goes.
Deduction-tracking checklist
Checkbox state isn't saved between visits (this is a static, no-account site) — treat this as a print/screenshot-friendly checklist, not a saved tracker.
Frequently asked questions
Do I need receipts for every single expense?
Generally yes for anything you plan to deduct, though the IRS does allow reasonable estimates in limited situations, like mileage, if a log wasn't kept but usage can be reconstructed credibly. Contemporaneous records are always the stronger position.
Can I deduct my home internet bill?
Only the business-use portion, generally based on a reasonable percentage of use, similar to how a vehicle's business-use percentage is calculated — not the full bill unless the connection is used exclusively for business.
What's the difference between a deduction and a tax credit?
A deduction reduces your taxable profit before tax is calculated; a credit reduces the tax bill itself, dollar for dollar. Credits are generally more valuable per dollar than deductions, though this guide focuses on deductions specifically.
Does taking the home office deduction increase my audit risk?
The IRS has historically flagged the home office deduction as an area of scrutiny, but a legitimate, well-documented claim that meets the regular-and-exclusive-use test is a normal part of many self-employed tax returns. Good documentation is the real protection, not avoiding the deduction altogether.
Can I deduct expenses from before I officially started the business?
Certain start-up costs incurred before the business began operating can sometimes be deducted or amortized under specific IRS rules, which are more limited than ordinary ongoing business deductions. This is a good specific question to bring to a tax professional.