Short answer
No federal law requires private employers to reimburse employee business mileage. Federal rules still matter in two ways: under 29 CFR 531.35, unreimbursed business expenses cannot push pay below minimum wage or overtime, and under 26 CFR 1.62-2 an IRS accountable plan keeps reimbursement out of wages. Some states require payment by statute, California and Illinois among them. Since 2018 most W-2 employees cannot deduct unpaid mileage, and the 2025 tax law made that suspension permanent (IRC §67(h)).
- No general federal reimbursement mandate: the FLSA regulates the minimum-wage effect of unreimbursed expenses, not reimbursement itself (29 CFR 531.35)
- The IRS standard mileage rate (76¢ Jul-Dec 2026) is a benchmark, not a federal payment requirement
- Accountable plans: business connection, substantiation and return of excess keep reimbursements excluded from wages (26 CFR 1.62-2)
- TCJA suspended unreimbursed employee business expenses for 2018-2025; P.L. 119-21 removed the end date, so the suspension is permanent (now IRC §67(h))
- Only narrow categories still deduct employee mileage: Armed Forces reservists, qualified performing artists, fee-basis officials, and impairment-related work expenses (Form 2106)
- A small number of states require private-employer reimbursement under state law, and the rest leave it to the written policy
The short answer: no federal reimbursement mandate
Federal law does not require private employers to pay for the business mileage an employee drives. The Fair Labor Standards Act sets minimum wage and overtime rules; it has no general expense-reimbursement provision.
The FLSA still matters indirectly. Under 29 CFR 531.35, wages must be paid 'finally and unconditionally or free and clear,' and a violation occurs in any workweek when required employee expenses cut into minimum or overtime wages. Business mileage that an employer requires but does not reimburse can have that effect in a low-pay or long-hours week.
The second federal hook is the overtime regular rate. Under 29 CFR 778.217, payments that reasonably approximate employer-incurred expenses are excluded from the employee's regular rate, which is why how a mileage payment is structured matters as much as whether one is made.
What the IRS requires: accountable plan rules
The IRS does not require employers to pay mileage, but it decides how a reimbursement is taxed. Under 26 CFR 1.62-2, an arrangement is an accountable plan only if it requires (1) a business connection for the expense, (2) substantiation of the amount, time, use, and business purpose, and (3) return of any amount paid above the substantiated expense.
Meet those three tests and the reimbursement is excluded from wages. Fail them by paying a flat allowance with no mileage record, and the payment is generally treated as wages subject to income tax, Social Security, and Medicare withholding.
The regulation's fixed-date safe harbor treats substantiation within 60 days and return of excess within 120 days as reasonable. Many employers use the IRS standard mileage rate to set and substantiate the payment; the IRS treats reimbursements at the standard rate as deemed substantiated for the mileage amount. For 2026 the business rate is 72.5¢ per mile for Jan-Jun and 76¢ for Jul-Dec.
What changed in 2018, and why it is permanent in 2026
The 2017 Tax Cuts and Jobs Act added IRC §67(g), which disallowed miscellaneous itemized deductions, including unreimbursed employee business expenses, for tax years 2018 through 2025. Before 2018, an employee who was not reimbursed could itemize work mileage on Form 2106 and Schedule A. That is why 'employee mileage reimbursement law 2018' remains a common search.
The 2025 reconciliation law (P.L. 119-21, §70110) removed the end date: it struck the phrase 'and before January 1, 2026' and renamed the heading from '2018 Through 2025' to 'Beginning After 2017'. The suspension was renumbered and now sits at IRC §67(h), applying to tax year 2026 and later.
The IRS states the effect in Publication 463: the cost of using your car as an employee 'will no longer be allowed to be claimed as an unreimbursed employee travel expense as a miscellaneous itemized deduction,' because the suspension applies to tax years beginning after 2017.
Who can still deduct employee mileage in 2026
A narrow set of employees can still deduct unreimbursed employee travel expenses, because their deductions are adjustments to income rather than itemized deductions. The 2026 Instructions for Form 2106 list four categories: Armed Forces reservists (members of a reserve component), fee-basis state or local government officials, qualified performing artists, and disabled employees with impairment-related work expenses.
If you are in one of those categories, deductible mileage is generally calculated at the standard mileage rate for the period of travel: 72.5¢ for Jan-Jun 2026 and 76¢ for Jul-Dec, claimed as an adjustment to income, not on Schedule A. Everyone else should treat a reimbursement shortfall as a policy or state-law question, not a federal deduction.
Which states require employers to reimburse mileage
- California. Labor Code §2802: 'An employer shall indemnify his or her employee for all necessary expenditures or losses incurred by the employee in direct consequence of the discharge of his or her duties.' Reimbursement awards carry interest.
- Illinois. 820 ILCS 115/9.5: employers must reimburse necessary expenditures within the scope of employment; employees generally must submit documentation within 30 calendar days, and unpaid amounts accrue a 5% monthly penalty.
- Massachusetts sets no mileage rate for private employers. The figure the state publishes covers travel to medical treatment under workers' compensation, and a private claim is decided by the written policy with the minimum wage as the floor.
- Most other states leave mileage to the employer's written policy. Check your handbook, and use the state-by-state overview to see the rules where you work.
What employees can do about unpaid mileage
If your employer does not pay for business mileage, the practical levers are usually policy and state law, not federal tax law. Check the written reimbursement policy, submit a dated mileage log with each claim, and keep a copy of everything you submit.
In states with reimbursement statutes, an unpaid claim can go to the state labor agency, which is the California Labor Commissioner or the Illinois Department of Labor in those two. Filing deadlines matter, so document each trip and each submission.
For tax purposes, treat an unpaid shortfall as non-deductible in 2026 for most employees, and keep the log in case a state claim or a future law change requires it. A complete log entry has four fields: date, destination, business purpose, and miles.