Mileage Reimbursement Audit 2026 by ReadyStack

The 2026 business mileage rate did not hold one value all year: 72.5 cents through June 30, 76 cents from July 1 (Announcement 2026-11). Most expense templates still hold one number.


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• Both 2026 rates, picked by the trip date — Uses 72.5 cents a mile for trips through June 30 and 76 cents from July 1, so a July report is not priced with January's number.
• The 60-day substantiation window — Flags a log handed in more than 60 days after the trip, which makes the entire payment taxable wages rather than only the part above the ceiling.
• The 120-day return-of-excess test — Separates a flat car allowance from substantiated miles and shows the amount that must come back within 120 days before it lands on the W-2.
• Employer payroll tax on the result — Stops Social Security at the 2026 wage base of $184,500 instead of charging 6.2 percent on everything, and adds Medicare at 1.45 percent.
• Exportable audit trail — Saves the inputs, the rate that was applied and the ruling as a .csv row you keep with the expense report.

| You type | |
|---|---|
| When the trip happened | default h2 |
| Business miles on this report | default 640 |
| Rate you actually reimbursed | default 72.5 |
| Flat allowance or advance also paid | default 250 |
| Days from the trip to the submitted log | default 21 |
| Excess was returned within 120 days | default False |
| Wages already paid to this employee in 2026 | default 62000 |

| It answers | |
|---|---|
| IRS rate for this period | cents/mile |
| Your rate against the IRS rate | cents/mile |
| Short of the IRS rate on these miles | $ |
| Tax-free ceiling | $ |
| Total you paid | $ |
| Above the ceiling | $ |
| Goes on the W-2 as wages | $ |
| Employer payroll tax on that | $ |
| Ruling | |

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