S Corp Mileage Deduction: Accountable Plan, Rates, and Logs

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.¹ Structure the reimbursement correctly and the owner receives the cash tax-free while the corporation deducts every dollar. Get it wrong and the entire amount converts to taxable wages, with income tax withholding and payroll taxes owed by both the owner and the corporation.

Personal Vehicle or S Corp-Owned Vehicle

The mechanics depend on who holds the title. Most S corp owners drive a personal vehicle for business and get reimbursed by the corporation. The owner tracks mileage, submits an expense report, and the corporation pays out at or below the standard mileage rate. The S corp deducts the payment; the owner takes it tax-free.

When the S corp itself owns the vehicle, the corporation deducts actual operating costs directly, and any personal use has to be reported as a taxable fringe benefit on the owner’s W-2.² The standard mileage rate is not available on a corporate-owned vehicle; you must use the actual expense method. For most owners driving a moderately priced vehicle, personal ownership with an accountable plan is the cleaner path. Corporate ownership tends to make sense mainly for heavy SUVs and trucks over 6,000 pounds that qualify for accelerated depreciation.

Why the Accountable Plan Is the Only Route

S corp owner-employees are treated as W-2 employees for tax purposes.³ Before 2018, an owner whose corporation failed to reimburse mileage could still claim the expense as a miscellaneous itemized deduction on their personal return. The Tax Cuts and Jobs Act suspended that deduction starting in 2018, and the One Big Beautiful Bill Act of 2025 made the elimination permanent. There is no fallback anymore.

So the accountable plan is the only mechanism that produces a tax benefit from business driving. Without one, any reimbursement the corporation pays is taxable wages, subject to federal income tax withholding plus Social Security and Medicare taxes on both sides of the payroll. A compliant 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 arrangement is an accountable plan only if it meets all three of the conditions below. Miss any one and every dollar reimbursed becomes taxable wages.⁴

Business connection. The expense must relate to services the owner-employee performs for the corporation, and the arrangement cannot pay out regardless of whether real business expenses were incurred.⁵

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 overpays, the owner must return the excess within 120 days.

These deadlines are IRS safe harbors rather than absolute limits, and a quarterly-statement alternative exists: the corporation issues statements at least every quarter showing unsubstantiated amounts, and the owner has 120 days from each statement to substantiate or repay.⁶ Staying inside the 60/120 windows keeps the plan unquestionably compliant.

Put the Plan in Writing

A written document is not technically required, but operating without one invites problems in an audit. The plan should state that reimbursements are limited to substantiated business expenses, spell out the submission process and deadlines, require the return of any excess, and identify the reimbursement rate (or say the corporation will follow the current IRS standard rate). Board minutes adopting the plan give the corporation something concrete to hand an examiner.

What Counts as Business Mileage

The IRS treats commuting and business travel as different categories, and it matters. Driving between your home and your regular workplace is commuting, and commuting is never deductible, regardless of distance or what you do on the drive.⁷ Owners who rent an office and drive there every morning often assume that trip counts because they own the business. It doesn’t.

Deductible driving starts when you leave your regular workplace for a business purpose: visiting a client, driving to a job site, picking up supplies, moving between work locations. Travel from your home to a temporary work location also qualifies, provided you have a regular office somewhere else.

The Home Office Exception

If your home office qualifies as your principal place of business, then travel from that home office to any other business location is deductible, regardless of distance.⁸ The home office must be used regularly and exclusively for business and must be where you conduct substantial administrative or management activities. A kitchen table where you check email in the evening does not qualify.

Mixed-Use Trips

If a business trip includes personal stops, only the business portion is deductible. Driving from your office to a client meeting and then continuing to a grocery store gives you deductible mileage from the office to the client, but the leg to the store comes out of the log. A brief coffee stop between two business destinations does not break the chain; anything more than a minimal personal detour does.⁹

Standard Mileage Rate or Actual Expenses

When the owner uses a personal vehicle, the corporation can reimburse under either method. They have different mechanics and different paperwork demands.

Standard Mileage Rate

The 2026 rate is 72.5 cents per business mile.¹ That figure covers depreciation, fuel, insurance, maintenance, and repairs in a single number. Parking fees and tolls are deductible on top of it. Multiply business miles by 72.5 cents, add tolls and parking, and you have the reimbursement.

Timing matters: the standard rate must be elected in the first year the vehicle is placed in business service.¹⁰ Start with actual expenses on a given vehicle and you cannot switch to the standard rate for that vehicle later. Going the other direction is allowed, though depreciation calculations have to be adjusted for the depreciation component already built into your earlier standard-rate deductions.

Actual Expense Method

Under actual expenses, you track every operating cost: 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. Drive 15,000 total miles with 10,000 for business and you deduct 66.7% of total vehicle costs. This method often produces a larger deduction on expensive vehicles with high operating costs, at the price of receipts for every category on top of the mileage log.

Keeping a Log That Holds Up

The IRS wants contemporaneous records, meaning you log each trip at or near the time it happens.⁹ Reconstructing a year of driving from memory in April is exactly the kind of record examiners discount. This is where most mileage deductions fall apart in practice.

Every entry needs four things:¹¹

Date of the trip.
Destination, identified specifically. Not “client office” but the name and location.
Business purpose. “Met with Johnson Industries to review Q3 contract” holds up; “business meeting” does not.
Miles driven for the business portion of the trip.

Track total annual miles too, business and personal, so you can compute a business-use percentage if the ratio is ever questioned or if you need to switch methods. Digital logs are acceptable, and GPS-based tracking apps generally record date, route, and distance automatically, which handles the contemporaneous requirement more reliably than manual entry. Whichever format you use, back it up. A crashed phone can erase your substantiation.

The log covers the numbers. Keep supporting documents that confirm business purpose too: calendar entries, meeting confirmations, email threads, client invoices tied to site visits. Under the actual expense method, keep receipts for every vehicle cost. That second layer is what separates a defensible deduction from one that collapses under examination.

How the Reimbursement Gets Reported

When the accountable plan works, reporting is clean. The S corporation deducts the total substantiated reimbursement as a business expense on Form 1120-S, typically on Line 19 (Other deductions).¹² The reimbursement does not appear on the owner’s W-2 and does not go on the owner’s Form 1040. The corporation gets the deduction. The owner gets the cash, tax-free. That is the point of the structure.

When the arrangement fails the accountable plan test, everything flips. The full reimbursement gets included as wages in box 1 of the W-2 and is subject to federal income tax withholding, Social Security tax (6.2% each side), and Medicare tax (1.45% each side).⁴ The corporation owes its matching employment taxes on top. And because unreimbursed employee expenses are no longer deductible on the personal return, the owner cannot recover the hit on their 1040.

If the S Corp Owns the Vehicle

The rules shift when the corporation holds the title. The standard mileage rate is off the table; the corporation deducts actual expenses and depreciates the vehicle over its useful life, subject to the Section 280F caps for passenger vehicles under 6,000 pounds.¹³ For passenger vehicles placed in service during 2026, the first-year cap is $20,300 with bonus depreciation or $12,300 without, followed by $19,800 in year two, $11,900 in year three, and $7,160 for each year after that. SUVs, trucks, and vans with a gross vehicle weight rating above 6,000 pounds sit outside those caps, which is why heavy SUVs show up so often on corporate returns.

Any personal use of a corporate-owned vehicle, including commuting, is a taxable fringe benefit that has to be valued and included in the owner’s W-2 wages in boxes 1, 3, and 5.² The IRS offers three valuation methods (cents-per-mile, commuting rule, and annual lease value), and the underlying mileage log that separates business from personal driving is what makes any of them work. Without one, an examiner can treat the entire use of the vehicle as a personal benefit.

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. The IRS has six years to audit if gross income is understated by more than 25%, so six years is the safer practice. If the corporation owns the vehicle and depreciates it, keep the vehicle records until at least three years after the tax year you dispose of the vehicle, because the depreciation history feeds the gain or loss on sale.¹⁴

1
Internal Revenue Service. IRS Sets 2026 Business Standard Mileage Rate at 72.5 Cents per Mile, Up 2.5 Cents
2
Internal Revenue Service. Publication 15-B (2026), Employer’s Tax Guide to Fringe Benefits
3
Internal Revenue Service. S Corporation Employees, Shareholders and Corporate Officers
4
eCFR. 26 CFR 1.62-2 – Reimbursements and Other Expense Allowance Arrangements
5
Internal Revenue Service. Revenue Ruling 2003-106 – Accountable Plans
6
U.S. Government Publishing Office. 26 CFR 1.62-2
7
eCFR. 26 CFR 1.274-14 – Disallowance of Deductions for Certain Transportation and Commuting Benefits
8
Internal Revenue Service. Revenue Ruling 99-7
9
Internal Revenue Service. Publication 463 (2025), Travel, Gift, and Car Expenses
10
Internal Revenue Service. Standard Mileage Rates
11
Office of the Law Revision Counsel. 26 USC 274 – Disallowance of Certain Entertainment, Etc., Expenses
12
Internal Revenue Service. Instructions for Form 1120-S (2025)
13
Internal Revenue Service. Rev. Proc. 2026-15
14
Internal Revenue Service. How Long Should I Keep Records