TL;DR. Most small business owners overpay on taxes because they lack documentation, not because they don't know about the deductions. The ten most commonly missed: home office, vehicle mileage, health insurance premiums, retirement contributions, business meals (50%), professional development and education, software subscriptions, business insurance, bank fees and interest, and Section 179 or bonus depreciation on equipment. The fix is systems. Mileage app, receipt capture, monthly categorization. Five-minute habits save thousands at tax time.
Every year, small business owners leave money on the table. Not because they're doing anything wrong, but because they don't know what they're allowed to deduct, or they know in theory but don't have the documentation to back it up.
We're not talking about aggressive tax strategies or gray-area loopholes. These are legitimate, well-established deductions that the IRS expects businesses to take. If you're not claiming them, you're overpaying your taxes. Here are the ones we see missed most often.
Home office deduction
If you use a dedicated space in your home regularly and exclusively for business, you can deduct a portion of your rent or mortgage, utilities, insurance, and repairs. The key words are "regularly" and "exclusively", a kitchen table you also eat dinner at doesn't count. A spare bedroom you use only as an office does.
There are two methods:
- Simplified method: $5 per square foot of your office, up to 300 square feet. Maximum deduction: $1,500. No tracking required beyond the square footage.
- Regular method: Calculate the percentage of your home used for business (office square footage ÷ total home square footage) and apply that percentage to your actual expenses. More work, but usually a bigger deduction.
Most people either don't know they qualify or think it triggers an audit. The IRS has explicitly said the home office deduction does not increase audit risk when properly documented. Take it.
Vehicle mileage
If you use your personal vehicle for business, client meetings, supply runs, bank deposits, anything that isn't commuting to a fixed office, you can deduct the business miles. For 2025 the standard mileage rate is 70 cents per mile (verify the current year's rate at irs.gov).
Drive 10,000 business miles in a year? That's a $7,000 deduction.
The catch: you need a log. The IRS requires contemporaneous records, date, destination, business purpose, and miles driven. "I drove a lot for work" doesn't cut it. Use an app like MileIQ, Everlance, or even a simple spreadsheet. Start tracking now, not at tax time.
Health insurance premiums
If you're self-employed and pay for your own health insurance (medical, dental, vision), the premiums are deductible. This isn't an itemized deduction, it's an above-the-line deduction on your personal return, which means you get it even if you take the standard deduction.
This applies to coverage for yourself, your spouse, and your dependents. It also includes long-term care insurance premiums (with age-based limits).
S-Corp owners: there's an extra step. The premiums need to be included on your W-2 as additional compensation, then deducted on your personal return. If your bookkeeper isn't handling this correctly, you're either missing the deduction or creating a compliance issue. This is one of those S-Corp-specific details that matters, and it ties into your reasonable compensation documentation.
Retirement contributions
Self-employed individuals have access to retirement accounts with significantly higher contribution limits than a traditional IRA. And every dollar you contribute is a dollar that reduces your taxable income.
- SEP IRA: Contribute up to 25% of net self-employment income, up to $69,000 (2024). Simple to set up, no employee matching requirements if you're solo.
- Solo 401(k): Contribute as both employee ($23,000 + $7,500 catch-up if over 50) and employer (25% of compensation). Total limit: $69,000. Best option if you're a high earner with no employees.
- SIMPLE IRA: Good if you have a few employees. Lower contribution limits but simpler administration.
The SEP IRA is the most popular choice for small business owners because you can set it up and fund it all the way up to your tax filing deadline (including extensions). So if you're reading this in March and haven't contributed yet, you still have time for last year. Verify current-year limits at irs.gov.
Business meals
Business meals are 50% deductible when they involve a business discussion with a client, prospect, or business associate. The meal doesn't have to be extravagant, but it does need to have a clear business purpose.
What you need to document:
- Date and location
- Who you met with
- What you discussed (a few words is fine, "discussed Q2 marketing plan with client")
- The receipt
A lot of business owners either expense everything (risky) or nothing (leaving money on the table). The right approach is somewhere in the middle: track every legitimate business meal with a quick note about who and why.
Professional development and education
Courses, conferences, certifications, books, and subscriptions that maintain or improve skills related to your current business are deductible. This includes:
- Online courses and workshops
- Industry conferences (including travel and lodging)
- Professional certifications and license renewals
- Trade publications and subscriptions
- Coaching and consulting fees
The key distinction: the education must relate to your current business or profession. An MBA program for a practicing consultant? Deductible. A law degree for someone who isn't a lawyer? Not deductible.
Software and subscriptions
Every SaaS tool you pay for to run your business is deductible. This adds up faster than most people realize:
- Accounting software (QuickBooks, FreshBooks)
- Project management (Asana, Monday, Notion)
- Communication (Zoom, Slack, Google Workspace)
- Design and marketing (Canva, Mailchimp, HubSpot)
- Cloud storage (Dropbox, Google Drive)
- Website hosting and domains
- Industry-specific software
Review your credit card and bank statements for recurring charges. You're probably paying for tools you've forgotten about, which is a separate problem, but everything you're actively using for business is a deduction.
Business insurance
Premiums for business-related insurance are deductible. This includes:
- General liability insurance
- Professional liability (E&O) insurance
- Commercial property insurance
- Business interruption insurance
- Cyber liability insurance
- Workers' compensation
If you work from home, a portion of your homeowner's or renter's insurance may also be deductible under the home office deduction (using the regular method).
Bank fees and interest
Business bank account fees, credit card processing fees, merchant fees, wire transfer fees, and interest on business loans are all deductible. These are small individually but add up over the year.
If you use Stripe, Square, or PayPal for payment processing, those fees are deductible. Check your year-end statements, the processing fee total is usually larger than you'd expect.
Depreciation of assets
When you buy equipment, furniture, or other assets for your business that last more than a year, you can depreciate them, spreading the deduction over the asset's useful life. Or, in many cases, you can deduct the entire cost in the year of purchase using Section 179 or bonus depreciation.
Common depreciable assets:
- Computers and monitors
- Office furniture (desks, chairs, shelving)
- Vehicles used for business
- Equipment and machinery
- Leasehold improvements
Section 179 lets you deduct up to $1,220,000 (2024) of qualifying equipment in the year you buy it. For most small businesses, this means you can write off the full cost of a new computer, desk, or vehicle immediately rather than spreading it over several years. Verify current-year limits before filing.
The real problem: documentation
Most missed deductions aren't missed because the business owner doesn't know about them. They're missed because there's no documentation. A mileage log that doesn't exist. Meal receipts that got thrown away. A home office that was never measured.
The fix is systems, not knowledge. Set up a mileage tracking app. Take a photo of every receipt (or use an app that does it automatically). Measure your home office once and write it down. These are five-minute tasks that save thousands at tax time.
This is also one of the biggest advantages of working with a bookkeeper. When your books are maintained monthly, deductions get categorized as they happen, not reconstructed from memory in March. Your bookkeeper catches the things you'd forget, and your tax return is built on clean data instead of guesswork. This is exactly the pattern behind our tax-ready books framework.
Key takeaways.
- The home office deduction does not increase audit risk when documented properly. Take it.
- Business miles at 70 cents each add up fast. 10,000 business miles is a $7,000 deduction, but only with a real log.
- S-Corp owner health insurance needs special W-2 handling. Run this past your bookkeeper and CPA.
- SEP IRA and Solo 401(k) limits are far higher than traditional IRAs. Contributing cuts your taxable income directly.
- Section 179 can let you write off a $10,000 computer or $40,000 vehicle in the year you bought it. Equipment isn't locked into multi-year depreciation unless you choose it.
Common questions
Does the home office deduction trigger an audit?
No. The IRS has publicly stated that the home office deduction, when properly documented, does not increase audit risk. The myth persists, but the data does not support it.
Simplified vs regular method for home office: which is better?
Simplified is easier (no tracking, capped at $1,500). Regular usually yields a larger deduction if you have significant home expenses (mortgage interest, utilities, insurance, maintenance). Calculate both your first year and choose the larger.
What's the current IRS standard mileage rate?
70 cents per business mile for 2025. The IRS updates this annually; confirm the current rate at irs.gov/tax-professionals/standard-mileage-rates before your next filing.
How do I track business mileage correctly?
Use a mileage app (MileIQ, Everlance, TripLog) that captures date, destination, business purpose, and miles automatically. The IRS requires contemporaneous records; reconstructing a year of mileage from memory in March is not defensible.
Are business meals 50% or 100% deductible?
50% for most business meals. Narrow exceptions (meals provided to employees on premises, food for company-wide events, certain de minimis fringe benefits) qualify for higher or full deductibility. Stick to 50% for ordinary client and prospect meals.
Can I deduct my phone bill?
The business-use portion. For a shared personal/business phone, document a reasonable business-use percentage and apply it to the monthly bill. A dedicated business line is 100% deductible.
Are clothing purchases deductible?
Only if the clothing is uniform-specific or required for the job and not wearable outside work (chef's coat, branded uniform, safety gear). Business suits, even if only worn to client meetings, are not deductible.
Is my car lease deductible?
The business-use portion is. You can use actual expenses (lease payments + fuel + insurance) prorated by business-use percentage, or the standard mileage rate. You must pick one method per vehicle per year and stick with it until the vehicle changes.
How do I deduct business startup costs?
Up to $5,000 in startup costs is deductible in the first year of business, if your total startup costs are $50,000 or less. Startup costs exceeding $5,000 amortize over 15 years. Track pre-opening expenses separately to claim them cleanly.
Can I deduct education or training?
Yes, if the education maintains or improves skills for your current business or profession. New-career training (a law degree if you're not a lawyer, for example) is not deductible.
What records do I need to support deductions?
Receipts, invoices, bank or credit card statements showing payment, and a clear business purpose. Keep everything seven years minimum to cover the IRS's six-year substantial-understatement window.
Should I deduct aggressively or conservatively?
Take every legitimate deduction with complete documentation. Don't claim deductions you can't defend. "Complete and documented" is the right posture, not "aggressive and thin."
Keep reading
- 5 Signs Your Books Aren't Tax-Ready
- S-Corp vs LLC: What Private Practice Owners Need to Know
- What Is Reasonable Compensation for S-Corp Owners?
- What Does a Monthly Bookkeeping Service Actually Do?
- Deduction review for private practices
Free look at your books
Not sure what you're missing? Book a free consult and we'll take a look at your books. No obligation, just an honest assessment of where you stand.