Methodology: Mileage Reimbursement Calculator
What this calculator gives you
This calculator estimates mileage reimbursement for business miles. You enter miles and the year of travel; the calculator applies the IRS business mileage rate for that year.
If you turn on California mode, it also compares the IRS-rate reimbursement with an estimated actual-cost amount. That comparison helps California employers see the possible Labor Code §2802 gap when actual driving costs are higher than the IRS rate.
The basic method
For IRS-rate reimbursement, the math is simple:
IRS-rate reimbursement = business miles x IRS business mileage rate for the travel year
For California actual-cost comparison, the calculator adds:
estimated actual cost = business miles x actual cost per mile
possible California gap = estimated actual cost minus IRS-rate reimbursement
The calculator's value is the rate table and the legal framing, not complex arithmetic.
Why the travel year matters
Use the rate for the year the miles were driven, not the year the reimbursement is paid.
Example: 1,000 business miles driven in 2025 and reimbursed in 2026 still use the 2025 IRS business rate of 70.0 cents per mile. The 2026 rate applies to miles driven on or after January 1, 2026.
If one mileage log crosses years, split it. December 2025 miles and January 2026 miles use different rates.
IRS business mileage rates
| Travel year | Business rate | Depreciation portion | Source |
|---|---|---|---|
| 2024 | 67.0 cents/mile | 30.0 cents/mile | IRS Notice 2024-08 |
| 2025 | 70.0 cents/mile | 33.0 cents/mile | IRS Notice 2025-5 |
| 2026 | 72.5 cents/mile | 35.0 cents/mile | IRS Notice 2026-10 |
The IRS business rate is optional for tax purposes. It is a standard rate for business use of a car, van, pickup, or panel truck. It is not the same as medical, moving, or charitable mileage.
California actual-cost comparison
California Labor Code §2802 requires employers to reimburse necessary business expenses. Under Gattuso v. Harte-Hanks Shoppers, Inc., 42 Cal.4th 554 (Cal. 2007), an employer may use an actual-expense method, a mileage-rate method, or a lump-sum method.
The IRS rate is usually a practical default, but it is rebuttable in California. If an employee can show actual necessary driving costs were higher, the employer may owe the difference.
Example: 1,000 California business miles in 2025.
| Method | Rate | Amount |
|---|---|---|
| IRS business rate | 70.0 cents/mile | $700.00 |
| AAA estimated actual cost | 77.18 cents/mile | $771.80 |
| Possible §2802 gap | 7.18 cents/mile | $71.80 |
The actual-cost field is editable. A compact EV may cost less than the IRS rate to operate; a truck in a high-insurance area may cost more.
In California mode, the calculator lets you choose the AAA weighted average, a 2025 AAA vehicle-category estimate, or a custom per-mile actual cost. The category estimates are not legal rates. They are a practical way to test whether the IRS rate is likely above or below a more realistic vehicle-cost benchmark.
Tax treatment
Mileage reimbursement at or below the IRS rate is generally excluded from W-2 wages if it is paid under an accountable plan. An accountable plan needs a business connection, timely substantiation, and return of any excess reimbursement.
Amounts above the IRS rate are generally taxable wages unless the employee substantiates higher actual costs. W-2 employees generally cannot deduct unreimbursed employee business expenses on their federal return, so under-reimbursement can be a real employee-cost issue.
What is not modeled
- Tax on above-rate reimbursement. The calculator flags that excess reimbursement can be taxable, but it does not compute payroll tax or income tax.
- FAVR plans. Fixed-and-variable-rate plans are employer reimbursement programs for higher-mileage drivers. They need a different setup than a simple miles x rate calculator.
- Medical, moving, or charitable mileage. Those rates are not employer business-mile reimbursement.
- Multi-year mileage logs. Split miles by year before using the calculator.
- Commuting. Home-to-regular-workplace commuting is not business mileage. The calculator assumes the miles entered are already business miles.
- Per diem, lodging, meals, and incidental expenses. Those use different IRS frameworks.
- Multi-state jurisdiction questions. California mode assumes California Labor Code §2802 applies to the mileage.
- Multiple vehicles in one period. If one employee used more than one vehicle, split the mileage by vehicle before using the category estimates.
Data sources
- IRS standard mileage rates index — IRS rate history.
- IRS Notice 2026-10 and IR-2025-128 — 2026 rate.
- IRS Notice 2025-5 — 2025 rate.
- IRS Notice 2024-08 — 2024 rate.
- 26 CFR §1.62-2 — accountable plans.
- 26 CFR §1.274-5 — substantiation.
- California Labor Code §2802 — California expense reimbursement.
- Gattuso v. Harte-Hanks Shoppers, Inc., 42 Cal.4th 554 (Cal. 2007) — California mileage/actual-expense/lump-sum methods.
- Commissioner v. Flowers, 326 U.S. 465 (1946) — commuting vs business travel.
- AAA "Your Driving Costs" 2025 and AAA 2025 brochure — actual-cost benchmarks used for the California comparison and vehicle-category estimates.
How accurate is this?
For a clean business-mile log in one travel year, the IRS-rate reimbursement is exact. The California actual-cost comparison is an estimate because actual costs depend on the employee's vehicle, insurance, location, financing, fuel, maintenance, and mileage pattern.
Use the calculator to size the reimbursement and spot possible California under-reimbursement. Use an accountable-plan process and actual records for payroll and tax treatment.
Frequently asked questions
Why is year of travel required instead of defaulting to the current year?
The single most common bug pattern for mileage calculators is assuming "current year." The IRS Notice for each year is effective for travel "on or after January 1, [year]" — a reimbursement paid in 2026 for miles driven in 2025 uses the 2025 rate (70¢), not 2026 (72.5¢). Surfacing year as a required input prevents the silent wrong-year math that produces under-reimbursement for back-pay scenarios and amended-return filings.
Why is California mode an explicit toggle, not derived from a state selector?
The jurisdictional question is "where does the employee perform the work," not "where is the employer based" or "where is the employee a resident." A California-based employer paying a Texas-remote worker doesn't trigger §2802; a Texas-based employer paying a California-remote worker does. A state dropdown would either ask the wrong question or require three separate fields (employer state, employee state, work-location state). The toggle lets the user assert the §2802 determination directly. Other state-based reimbursement statutes (Illinois 820 ILCS 115/9.5, Montana §39-2-701, etc.) have similar mechanics but lack the Gattuso "presumptively reasonable but rebuttable" doctrine that makes the IRS-vs-actual comparison the dominant compliance question.
Why does California mode default to the AAA weighted-average per-mile figure?
AAA's "Your Driving Costs" report is the most-cited Tier-2 source for actual vehicle operating costs in litigation and practitioner guidance. The 2025 weighted-average ($11,577/year ÷ 15,000 miles = 77.18¢/mile) covers depreciation, fuel, maintenance/repair/tires, insurance, license/registration/taxes, and finance charges — the same conceptual basket the IRS Notice uses for its rate-setting. The per-mile figure is overridable: an EV driver runs much lower (≈ 15–20¢ for operating cost), a pickup driver runs much higher (≈ 99¢ total). The default surfaces the population average; the override lets a specific employee's situation come through.
Why does the 2026 California mode fall back to the 2025 AAA figure?
AAA publishes the "Your Driving Costs" report annually in September. The 2026 report typically becomes available in September 2026 — until then, the calculator falls back to the most recent published year (2025's 77.18¢/mile) and discloses the fall-back inline ("AAA 2026 not yet published"). The fallback is conservative: the 2025 figure was a $719 decline from 2024, and longer-run AAA averages have been trending up with vehicle prices and insurance premiums, so the 2025 figure is more likely to under-state than over-state 2026 actuals.
Why isn't the medical / moving / charitable rate surfaced?
Those are taxpayer-side tax-return deductions, not employer reimbursement scenarios. The IRS publishes all four rates in the same Notice but they're conceptually distinct: medical (20.5¢ in 2026) is a Schedule A deduction subject to the 7.5%-of-AGI floor; moving (20.5¢) is narrowly available to active-duty military and intelligence-community personnel only per OBBBA §70113(b); charitable (14¢) is the donation mileage deduction fixed by 26 USC §170(i) since 1998. None of these are employer-reimbursement math. The calculator is scoped to the business-rate reimbursement scenario for clarity.
Why doesn't this calculator surface FAVR plan math?
Fixed-and-Variable-Rate plans under Rev. Proc. 2010-51 are an IRS-blessed alternative to flat mileage reimbursement for high-mileage drivers (typically 25,000+ business miles/year — outside sales, pharmaceutical reps, field service). FAVR has a two-component structure: a fixed monthly stipend covering depreciation/insurance/registration in the rep's geography, plus a variable per-mile rate for fuel and maintenance. The 2026 maximum standard automobile cost under FAVR is $61,700. The math requires substantially more inputs (employer's geography, vehicle category, fixed/variable split formula) and would clutter the worker-facing flat-rate scenario this calculator addresses. A future FAVR-specific calculator would be a separate tool.
About Clockspot
Clockspot helps small businesses track employee time and keep payroll-ready records. Used in all 50 states since 2007, we focus on getting time and pay right — including the wage-and-hour rules that shape both.
Clockspot helps small businesses keep clock events, job/location context, corrections, approvals, and payroll-ready time records connected. Use those records alongside your mileage logs and reimbursement policy. See how Clockspot keeps field time records organized.