An S corporation deducts business mileage by reimbursing the owner-employee through a written accountable plan and then claiming that reimbursement as a business expense on Form 1120-S. For 2026, the IRS standard mileage rate is 72.5 cents per business mile.1Internal Revenue Service. IRS Sets 2026 Business Standard Mileage Rate at 72.5 Cents per Mile, Up 2.5 Cents Done correctly, the corporation gets the deduction and the owner receives the cash tax-free. Done incorrectly, the entire reimbursement gets reclassified as taxable wages, triggering income tax and payroll taxes for both sides.
Who Should Own the Vehicle
The S corp mileage deduction works differently depending on who holds the title. Most owner-employees use a personal vehicle and get reimbursed by the corporation. The owner tracks mileage, submits expense reports, and the S corp pays at or below the standard rate under an accountable plan.
When the S corp itself owns the vehicle, the corporation deducts actual operating costs directly (fuel, insurance, maintenance, depreciation), but any personal use must be reported as a taxable fringe benefit on the owner’s W-2.2Internal Revenue Service. Publication 15-B (2026), Employer’s Tax Guide to Fringe Benefits Corporate-owned vehicles also cannot use the standard mileage rate; the actual expense method is required, and annual depreciation caps apply to passenger vehicles. For most owners driving a moderately priced car, personal ownership with an accountable plan reimbursement is cleaner. Corporate ownership tends to pay off only for heavy trucks or SUVs over 6,000 pounds that qualify for accelerated depreciation.
The rest of this article focuses on the personal-vehicle-plus-reimbursement path, which is where almost all S corp mileage deductions live.
Why an Accountable Plan Is the Only Option
S corp owner-employees are treated as W-2 employees for tax purposes.3Internal Revenue Service. S Corporation Employees, Shareholders and Corporate Officers Before 2018, an owner who paid business driving expenses out of pocket could at least claim an unreimbursed employee expense deduction on Schedule A. The Tax Cuts and Jobs Act suspended that deduction, and the One Big Beautiful Bill Act of 2025 made the elimination permanent. There is no longer any personal return deduction for unreimbursed business mileage.
That leaves the accountable plan as the only mechanism for turning business driving into a tax benefit. Without one, the corporation can still cut the owner a check for mileage, but those payments are taxable wages, subject to federal income tax, Social Security, and Medicare withholding, with the corporation owing its matching employment tax share. A properly structured accountable plan converts that same payment into a tax-free reimbursement for the owner and a deductible business expense for the corporation.
The Three Accountable Plan Requirements
An accountable plan must satisfy three conditions. Fail any one of them and the entire arrangement becomes a non-accountable plan, which means every dollar reimbursed is taxable wages.4eCFR. 26 CFR 1.62-2 – Reimbursements and Other Expense Allowance Arrangements
- Business connection. The expense must relate to services the owner-employee performs for the S corporation. The arrangement cannot pay reimbursements regardless of whether real business expenses were incurred.5Internal Revenue Service. Revenue Ruling 2003-106 – Accountable Plans
- Substantiation. The owner must document the amount, date, destination, and business purpose of each trip and submit that documentation to the corporation within 60 days.
- Return of excess. If the corporation advances funds or reimburses more than the substantiated expenses, the owner must return the excess within 120 days.
The 60-day and 120-day windows are IRS safe harbors rather than absolute limits, but staying inside them keeps the plan unquestionably compliant.6U.S. Government Publishing Office. 26 CFR 1.62-2 A quarterly statement option also exists: the corporation issues statements at least every quarter showing unsubstantiated amounts, and the owner has 120 days from each statement to substantiate or return the excess.
Put It in Writing
The IRS does not technically require a written accountable plan document, but operating without one invites trouble in an audit. A sound written plan states that reimbursements are limited to business expenses, describes the substantiation process and deadlines, requires the return of excess payments, and specifies the reimbursement rate (or ties it to the current IRS standard rate). Keeping that document on file demonstrates intent to comply and gives an examiner something concrete to review.
What Counts as Business Mileage
The IRS draws a hard line between commuting and business travel. Driving between your home and your regular workplace is commuting, and it is never deductible, no matter the distance or whether you take business calls on the way.7eCFR. 26 CFR 1.274-14 – Disallowance of Deductions for Certain Transportation and Commuting Benefits This catches S corp owners who rent an office, drive there each morning, and assume the drive is deductible because they own the business. It isn’t.
Deductible mileage starts once you leave your regular workplace for a business purpose: visiting a client, traveling to a job site, picking up supplies, driving between two work locations. Travel from your home to a temporary work location also counts, as long as you have a regular office elsewhere.
The Home Office Exception
If your home office qualifies as your principal place of business, all travel from that home office to any other business location is deductible, regardless of distance.8Internal Revenue Service. Revenue Ruling 99-7 The space must be used regularly and exclusively for business, and it must be where you conduct substantial administrative or management activities. A kitchen table where you occasionally check email doesn’t qualify.
Mixed-Use Trips
When a business trip includes personal stops, only the business portion is deductible. If you drive from your office to a client meeting and then continue to a grocery store, the office-to-client mileage counts and the detour does not. A brief coffee stop between two business destinations doesn’t break the chain, but anything more than a minimal personal detour does.9Internal Revenue Service. Publication 463 (2025), Travel, Gift, and Car Expenses
Standard Mileage Rate or Actual Expenses
When the owner uses a personal vehicle, the S corp can reimburse under either method. Each has different requirements and suits different situations.
Standard Mileage Rate
The 2026 rate is 72.5 cents per business mile. That number rolls depreciation, fuel, insurance, maintenance, and repairs into a single figure. Parking fees and tolls are deductible on top. Simplicity is the main appeal: multiply business miles by the rate, add tolls and parking, and that is your deductible reimbursement.
Timing matters. The standard mileage rate must be elected in the first year the vehicle is placed in service for business.10Internal Revenue Service. Standard Mileage Rates Start with actual expenses and you cannot switch to the standard rate for that vehicle later. You can switch from the standard rate to actual expenses in a later year, though depreciation calculations have to be adjusted for the depreciation component already built into prior standard-rate deductions.
Actual Expense Method
Under the actual expense method, you track every cost of operating the vehicle: fuel, oil changes, tires, repairs, insurance, registration, and either depreciation or lease payments. You then multiply the total by your business-use percentage from your mileage log. If you drove 15,000 total miles and 10,000 were for business, your business-use percentage is 66.7%, and that fraction of total vehicle costs is deductible.
This method tends to produce a larger deduction for expensive vehicles with high operating costs, at the price of significantly more paperwork, since receipts for every expense category are required on top of the mileage log.
Records That Survive an Audit
The IRS requires contemporaneous records, meaning each trip is logged at or near the time it happens.9Internal Revenue Service. Publication 463 (2025), Travel, Gift, and Car Expenses Reconstructing a year’s worth of driving from memory in April is exactly the kind of record the IRS discounts. This is where most mileage deductions fall apart in practice: the owner drove 20,000 business miles but can’t produce a log that was maintained throughout the year.
What Each Entry Needs
Every trip in your mileage log must include four elements:11Office of the Law Revision Counsel. 26 USC 274 – Disallowance of Certain Entertainment, Etc., Expenses
- The specific date of the trip.
- The destination, with name and location rather than a generic label.
- The business purpose. “Met with Johnson Industries to review Q3 contract” is strong; “business meeting” is weak.
- Miles driven, from odometer readings or GPS-verified distance for the business portion.
Track your total miles for the year as well, both business and personal, so you can calculate the business-use percentage if you ever need to switch methods or defend the ratio.
Digital Logs and Backup
The IRS accepts digital mileage logs, and GPS-based tracking apps have largely replaced paper notebooks. These apps automatically record the date, route, and distance for each trip, satisfying the contemporaneous recording requirement more reliably than manual entry. Whatever format you use, back it up. A crashed phone or lost notebook can wipe out your substantiation entirely.
Supporting Documentation
The mileage log covers the quantitative side. Keep documents that confirm the business purpose too: calendar entries, email chains confirming meetings, appointment confirmations, and client invoices tied to site visits. Under the actual expense method, also retain every receipt for fuel, repairs, insurance, and other vehicle costs. This second layer of evidence is what separates a defensible deduction from one that crumbles under examination.
Reporting on Both Returns
When the accountable plan works, reporting is simple. The S corporation deducts the substantiated reimbursement as a business expense on Form 1120-S, typically on Line 19 (Other deductions).12Internal Revenue Service. Instructions for Form 1120-S (2025) Because the payment was made under an accountable plan, it does not appear on the owner’s W-2 and the owner does not report it as income on Form 1040. The corporation gets the deduction, the owner gets the cash, and no payroll tax is owed on either side.
If the arrangement fails any of the three accountable plan tests, the reporting flips. The full reimbursement becomes wages in box 1 of the owner’s W-2 and is subject to federal income tax, Social Security tax (6.2% each for employer and employee), and Medicare tax (1.45% each).4eCFR. 26 CFR 1.62-2 – Reimbursements and Other Expense Allowance Arrangements The corporation owes its matching employment tax share. Since unreimbursed employee expenses are permanently non-deductible on personal returns, the owner cannot recover any of that tax hit on the 1040. The stakes of getting the accountable plan wrong are measurable, and they show up on every affected paycheck and tax return.
How Long to Keep the Records
Keep mileage logs, expense receipts, and accountable plan documentation for at least three years after filing the return that claims the deduction. If you underreport gross income by more than 25%, the IRS has six years to audit, so the safer practice is to hold records for six years.13Internal Revenue Service. How Long Should I Keep Records If the S corp owns the vehicle and claims depreciation, keep all vehicle records until at least three years after the tax year you dispose of the vehicle, since the depreciation history affects the gain or loss calculation on sale.