If you own an S-corporation, you chose one of the most tax-efficient business structures available. But that efficiency only works if you use it correctly — and most S-corp owners I meet are leaving thousands of dollars on the table every year without realizing it.
After decades managing tax strategy for Fortune 500 companies and now working directly with small business owners, I see the same mistakes over and over. Here are the five most costly ones — and what to do about them.
Mistake 1: Paying Yourself the Wrong Salary
The IRS requires S-corp owner-employees to pay themselves a ‘reasonable compensation’ before taking distributions. Many owners underpay their salary to minimize payroll taxes — but this is one of the IRS’s most scrutinized areas.
The fix: Work with a CPA to determine a defensible reasonable salary based on your industry, role, and revenue. Getting this wrong can trigger back payroll taxes, penalties, and interest.
Mistake 2: No Retirement Plan
S-corp owners can contribute significantly more to retirement accounts than W-2 employees. A Solo 401(k) or SEP-IRA can reduce your taxable income by $23,000 to $69,000 per year depending on your situation — yet many owners never set one up.
The fix: Establish a retirement plan before December 31st. This is one of the highest-impact moves you can make before year-end.
Mistake 3: Missing the Home Office Deduction
If you use a portion of your home exclusively for business, you may qualify for the home office deduction. Many S-corp owners skip this because they think it’s too complicated or triggers audits. Neither is true when done correctly.
The fix: Calculate your dedicated workspace square footage as a percentage of your home and deduct the proportionate share of rent or mortgage, utilities, and insurance.
Mistake 4: Not Tracking Mileage and Vehicle Use
Business use of your vehicle is deductible — but only if you track it. Many owners estimate or skip this entirely, leaving hundreds or thousands in deductions unclaimed.
The fix: Use a mileage tracking app like MileIQ or Everlance. The IRS standard mileage rate for 2026 is 72.5 cents per mile for business travel.
Mistake 5: Waiting Until April to Talk to Your CPA
Tax filing and tax planning are two completely different things. If you only talk to your CPA during tax season, you’re getting compliance — not strategy. The best tax savings opportunities close on December 31st.
The fix: Schedule a mid-year tax review every year. A one-hour conversation in September or October can identify moves that save you significantly before the year closes.
The Bottom Line
S-corp status gives you a powerful tax advantage — but only if you manage it actively. If you haven’t reviewed your salary structure, retirement contributions, or deduction strategy recently, there’s a good chance you’re overpaying.
