The average small business owner who doesn't work with a CPA misses thousands of dollars in legitimate tax deductions every year. Not because the deductions don't exist — but because nobody told them what to claim.
Here are the 10 deductions most commonly left on the table, with real dollar amounts showing what they cost you.
1. Home Office Deduction (Actual Method)
Most home-based business owners either skip the home office deduction entirely or use the simplified method ($5/sq ft, max $1,500). The actual expense method — calculating the real percentage of rent, utilities, insurance, and repairs — typically produces $2,500-$5,000+ in deductions.
What you're missing: $1,000-$3,500 per year in additional deductions over the simplified method.
2. Vehicle Expenses
Many business owners forget to track mileage or don't realize how much they drive for business. At 67 cents per mile, even 8,000 business miles per year is a $5,360 deduction.
The key is a mileage log. Without one, the entire deduction is disallowed in an audit. Start tracking today — apps like MileIQ make it automatic.
What you're missing: $2,000-$8,000+ per year depending on how much you drive.
3. Retirement Plan Contributions
A Solo 401(k) allows up to $70,000 in annual contributions. A SEP-IRA allows up to 25% of net income. These deductions are massive — and many business owners either don't know about them or don't contribute enough.
What you're missing: $5,000-$70,000 in deductions, saving $1,200-$25,000+ in taxes.
4. Health Insurance Premiums
Self-employed individuals can deduct 100% of health insurance premiums for themselves, their spouse, and dependents. This is an above-the-line deduction — available even if you don't itemize.
If you're paying $800/month for family coverage, that's a $9,600 deduction many self-employed people don't realize they can take.
What you're missing: $3,000-$15,000+ per year.
5. Qualified Business Income (QBI) Deduction
Pass-through business owners can deduct up to 20% of qualified business income. On $100,000 in QBI, that's a $20,000 deduction — saving $4,400 at the 22% bracket.
Many business owners miss this because their tax software doesn't calculate it correctly, or they don't realize they qualify.
What you're missing: $2,000-$15,000+ per year.
6. Business Use of Phone and Internet
Your phone and internet bills are partially deductible based on business-use percentage. If 60% of your phone use is business-related and your annual bill is $1,800, that's a $1,080 deduction.
What you're missing: $500-$1,500 per year.
7. Professional Development and Education
Courses, certifications, conferences, books, online learning platforms, industry memberships — anything that maintains or improves skills in your current business is deductible.
What you're missing: $500-$3,000+ per year.
8. Software Subscriptions
QuickBooks, Adobe, Zoom, Slack, Canva, cloud storage, CRM tools, email marketing, cybersecurity — add up every subscription you use for business. Most owners forget at least a few.
What you're missing: $500-$3,000 per year.
9. Bank Fees and Processing Costs
Stripe fees, PayPal fees, Square charges, monthly bank fees, credit card annual fees (business cards), wire transfer fees — these small amounts add up over a year.
What you're missing: $500-$2,000 per year.
10. The S-Corp Election Itself
This isn't a deduction — it's a structural change that eliminates self-employment tax on distributions. A business earning $120,000 saves $6,000-$10,000 per year by electing S-Corp status instead of operating as a sole proprietor.
Most business owners don't know about this, don't understand the math, or think it's too complicated. A CPA sets it up and handles the compliance.
What you're missing: $5,000-$15,000+ per year.
The Total Cost of Missing These Deductions
Add it up. A business owner missing even half of these deductions is leaving $10,000-$30,000 in tax savings on the table annually. At a 30% combined tax rate, that's $3,000-$9,000 more in taxes than necessary.
A CPA who specializes in small business tax typically costs $500-$2,000 for annual tax preparation and planning. The return on that investment is 3x to 10x or more.
Stop leaving money on the table. Find a CPA who knows small business deductions inside and out at ListMyCpa.com. Search by state, city, and specialization to find the right match.