Here’s the governing rule: you can write off business expenses that are “ordinary and necessary” for your trade or business, meaning common in your field and helpful for running it. In practice, that covers a wide range: mileage, a home office, software, insurance, equipment, professional fees, marketing, and more. The catch is that the expense must be genuinely business-related and properly documented. Guessing or blurring personal and business spending is how deductions get disallowed.
One note before we dig in: tax rules change and depend heavily on your situation, entity type, and location. I’m not a tax advisor, and this is general information, not personalized advice, so confirm anything significant with a qualified tax professional before you file.
Key Takeaways
- The standard is “ordinary and necessary” for your business.
- 2026 mileage rate: 72.5 cents per business mile.
- Home office (simplified): $5 per square foot, up to 300 sq ft, so a $1,500 maximum.
- Section 179 lets you expense large equipment purchases immediately rather than depreciate them.
- Documentation is everything; without records, the IRS can still deny a legitimate deduction.
The Most Common Write-Offs
Most small businesses have more deductible expenses than they claim, usually because they simply forget to track them. Here are the most important ones, with current figures where they apply.
| Expense | 2026 detail |
|---|---|
| Vehicle mileage | 72.5 cents per business mile (standard rate) |
| Home office (simplified) | $5/sq ft, up to 300 sq ft ($1,500 max) |
| Equipment & software | Section 179 immediate expensing available |
| Software & subscriptions | Fully deductible if business-use |
| Professional fees | Legal, accounting, consulting |
| Marketing & advertising | Fully deductible |
| Business insurance | Fully deductible |
| Payment processing fees | Fully deductible |
The avoidance of taxes is the only intellectual pursuit that still carries any reward.
— John Maynard Keynes
Worth being precise here: avoidance (legally minimizing what you owe) is entirely different from evasion (illegally hiding what you owe). Claiming every deduction you’re legitimately entitled to is smart and expected; inventing them is fraud.
The Home Office Deduction People Wrongly Fear
A persistent myth says claiming a home office triggers an audit. It doesn’t, as long as you actually qualify. The requirement is that the space is used regularly and exclusively for business, so a dedicated room or clearly defined area, not the kitchen table where you also eat dinner. The simplified method is easy: $5 per square foot up to 300 square feet, capped at $1,500, with almost no record-keeping. The regular method (deducting an actual percentage of rent, utilities, and insurance) can yield a bigger deduction but requires more documentation. If you legitimately work from home, claim it.
Big Purchases: Section 179 and Bonus Depreciation
Normally, you would depreciate a large asset like a vehicle or machinery over several years. Section 179 lets you deduct the full cost in the year you buy it, and the 2026 limits are generous enough that virtually any small business purchase qualifies. Bonus depreciation offers a similar immediate write-off for qualifying property. The strategic point: timing matters. Buying needed equipment before year-end can shift a significant deduction into the current tax year, though you should never buy something you don’t need just to get a deduction, since you’re still spending a dollar to save a fraction of it.
A Realistic Example of Missed Deductions
Consider an illustrative case. Priya, a freelance consultant, dutifully deducted her laptop and software but assumed the rest was “too small to bother with.” When she finally tracked things properly for a year, she found she’d been missing: roughly 6,000 business miles (worth about $4,350 at 72.5 cents), a qualifying 120-square-foot home office ($600 under the simplified method), her professional liability insurance, her accountant’s fee, payment processing fees on client invoices, and the portion of her phone and internet used for business.
Together, these added several thousand dollars in legitimate deductions she’d simply never claimed. She didn’t do anything aggressive or clever; she just started tracking. That’s the most common small-business tax mistake: not fraud, just neglect.
What You Generally Can’t Write Off
Some things are off-limits or heavily restricted, and getting these wrong causes real problems. Personal expenses aren’t deductible, even if you’d like them to be. Commuting from home to a regular workplace is personal, not business, mileage. Clothing is only deductible if it’s genuinely unsuitable for everyday wear (a uniform or safety gear, not a nice suit). Client entertainment is largely non-deductible, though business meals may be partially deductible.
And fines and penalties are never deductible. When something feels like a stretch, it usually is.
Frequently Asked Questions
What does “ordinary and necessary” actually mean?
“Ordinary” means common and accepted in your line of business; “necessary” means helpful and appropriate for it. The expense doesn’t have to be indispensable, but it must be genuinely business-related rather than personal.
Can I write off my car?
You can deduct business use of your vehicle, either using the standard mileage rate (72.5 cents per mile in 2026) or actual expenses proportional to business use. Commuting to a regular workplace doesn’t count, and you must keep a mileage log.
Does claiming a home office trigger an audit?
No, this is a myth. As long as the space is used regularly and exclusively for business and you can document it, the home office deduction is a legitimate write-off that many self-employed people are entitled to claim.
What records do I need to keep?
Keep receipts, invoices, bank and card statements, and a mileage log, typically for several years. Using a separate business bank account and accounting software makes documentation nearly automatic, which is your best protection if you’re ever questioned.
The Bottom Line
You can write off expenses that are ordinary and necessary for your business, including mileage at 72.5 cents per mile in 2026, a home office at $5 per square foot up to $1,500, equipment via Section 179, software, insurance, professional fees, and processing costs. Most owners under-claim simply because they don’t track.
Keep clean records, separate business from personal spending, and don’t stretch into gray areas. And since tax rules shift and depend on your circumstances, run anything significant past a qualified tax professional. This is general information, not tax advice.
Image Credit: Nataliya Vaitkevich; Pexels
