You bought supplies on your personal card. You drove your own car to a job site. You paid for a business lunch in cash and never logged it. Every one of those transactions was a real, deductible business cost—and if you never ran it through your books, the IRS never saw it. That means you paid income tax on money that should have reduced your taxable income. It's a quiet, slow leak that catches up with owners every April.
The fix isn't complicated, but it requires a system. Here's what's actually happening, why it matters more for certain business structures, and exactly how to stop it.
What Is an Unreimbursed Business Expense, and Why Does It Matter?
An unreimbursed business expense is any ordinary and necessary cost you pay personally—rather than through a business account—and never formally record or pay back through your company. The IRS allows deductions for ordinary and necessary business expenses under IRC § 162, but you only capture that deduction if the expense actually flows through your business books.
When an expense never hits your business records, it effectively disappears. Your business income looks artificially high, your tax bill goes up, and the IRS collects tax on money you already spent on the business. For a sole proprietor in Indiana paying both federal self-employment tax (15.3% on net earnings up to the Social Security wage base) and Indiana's individual income tax rate, even a few hundred dollars in missed deductions each month compounds into a significant overpayment by year-end.
Does Your Business Structure Change How This Works?
Yes—your entity type determines exactly how you recover out-of-pocket costs, and the stakes are highest for S-corp owners who skip a formal reimbursement plan.
Sole proprietors and single-member LLCs (taxed as disregarded entities) file Schedule C. Any business expense you pay personally can be added directly to Schedule C as long as you have documentation. The process is forgiving, but it requires you to actually capture the expense at tax time.
Partnerships and multi-member LLCs have more complexity. Partners generally cannot deduct unreimbursed partnership expenses on their personal returns unless the partnership agreement explicitly allows it—and even then, the rules are narrow. The cleanest solution is a formal reimbursement policy at the partnership level.
S-corporation owners face the strictest situation. Because an S-corp is a separate legal entity, expenses you pay personally are not automatically the corporation's expenses. If the corp doesn't reimburse you, those costs vanish. Worse, if you try to deduct them on your personal return, you'll likely find you have no mechanism to do so under current law. This is why S-corp tax planning almost always includes setting up an accountable plan.
What Is an Accountable Plan, and Do You Need One?
An accountable plan is a formal reimbursement arrangement between you (as employee or owner-employee) and your business that satisfies IRS requirements, making reimbursements tax-free to you and fully deductible by the company. If your plan doesn't meet IRS rules, reimbursements become taxable wages—defeating the purpose entirely.
To qualify as an accountable plan under Treasury Regulation § 1.62-2, the arrangement must meet three tests:
Business connection: The expense must have a clear, ordinary-and-necessary business purpose.
Substantiation: You must provide receipts, mileage logs, or other records within a reasonable time (the IRS safe harbor is 60 days after the expense is incurred).
Return of excess: Any advance or reimbursement over the actual expense must be returned to the company within 120 days.
An accountable plan doesn't need to be a long legal document. A one-page written policy, consistently followed, is enough. What it does need is consistent execution—submit your receipts, get reimbursed by check or ACH from the business account, and record it in your books. That paper trail is your protection if the IRS ever questions it.
If you're unsure whether your current setup qualifies, our tax planning service includes a review of your reimbursement structure.
What Expenses Are Commonly Missed by Small Business Owners?
Most owners know to track big purchases, but the chronic leaks are usually small and frequent. Here are the categories we see missed most often at Warrior Business Services, especially among NE Indiana trades, manufacturers, and family-owned businesses:
Mileage and vehicle costs: The IRS standard mileage rate changes annually. Owners who drive personal vehicles for business—client visits, supply runs, job sites—often have no mileage log and claim nothing.
Home office: If you use part of your home regularly and exclusively for business, a portion of your mortgage interest, rent, utilities, and insurance may be deductible. Many owners skip this because it feels complicated.
Cell phone and internet: The business-use percentage of your personal phone and home internet bill is deductible. Most owners pay 100% personally and deduct 0%.
Business meals: Currently deductible at 50% when they meet the IRS business purpose test. Owners frequently pay cash, save no receipt, and lose the deduction entirely.
Tools, software, and subscriptions: Small purchases made on a personal card—a $15 app, a $40 tool—add up to hundreds or thousands annually and are rarely captured.
Professional development: Continuing education, trade publications, and licensing fees related to your field are deductible and often overlooked.
How Do You Set Up a Simple Reimbursement System Starting Today?
You don't need an expensive software platform. A straightforward three-step process works for most small businesses in Indiana:
Write a one-page accountable plan policy. State that the business will reimburse owner and employee business expenses that have a business purpose and are substantiated with receipts within 60 days. Your CPA at Warrior can draft this for you in minutes.
Submit expenses on a simple log. A spreadsheet or free expense app works. Date, amount, vendor, business purpose, and a photo of the receipt. Submit monthly at minimum.
Cut a reimbursement from the business account. Don't just make a journal entry. Actually transfer the money from the business checking account to your personal account and record it as "reimbursement—accountable plan" in your books. This creates the paper trail that proves the transaction was real.
If your books are behind and you have months of personal-card business expenses sitting uncaptured, that's a cleanup problem worth solving now—not at tax time. Our cleanup and catch-up bookkeeping service is built exactly for this situation.
How Much Could This Actually Save You?
The answer depends on your volume of missed expenses, your entity type, and your marginal tax rates—but the math is straightforward. If you're an S-corp owner in Indiana who misses $500/month in reimbursable expenses, that's $6,000 per year in gross income that gets taxed unnecessarily. At a combined federal and Indiana effective rate of roughly 30–35% (varying by your situation), you could be overpaying $1,800–$2,100 per year on expenses that were already legitimate deductions. Over five years, that's real money—and it doesn't account for the self-employment tax savings that flow through proper S-corp structuring.
The fix costs almost nothing to implement. The failure to implement it costs you every single year. If you're not sure what you've been missing, reach out to Warrior Business Services and we'll take a look.
Sources
26 U.S. Code § 162 – Trade or Business Expenses. Internal Revenue Code. https://www.irs.gov/publications/p535
Self-Employment Tax (Social Security and Medicare Taxes). Internal Revenue Service. 2024. https://www.irs.gov/businesses/small-businesses-self-employed/self-employment-tax-social-security-and-medicare-taxes
Indiana Individual Income Tax Overview. Indiana Department of Revenue. 2024. https://www.in.gov/dor/individual-income-taxes/
Publication 463: Travel, Gift, and Car Expenses – Accountable Plans. Internal Revenue Service. 2023. https://www.irs.gov/publications/p463
IRS Standard Mileage Rates. Internal Revenue Service. 2024. https://www.irs.gov/tax-professionals/standard-mileage-rates
Publication 587: Business Use of Your Home. Internal Revenue Service. 2023. https://www.irs.gov/publications/p587
Written by
Warrior Business Services
Warrior Business Services is a boutique CPA firm in downtown Fort Wayne, Indiana, advising family-owned businesses and growth-minded owners across Northeast Indiana.