$227.60 of a $714.00 mileage report becomes W-2 wages, and the US bookkeeper who keyed it did nothing unusual: they paid 640 business miles at 72.5 cents and added the $250 monthly car allowance, exactly as the template has said all year.
The template is wrong from July 1.
The IRS set the 2026 business standard mileage rate at 72.5 cents a mile in Notice 2026-10. Then, on the back of a roughly 38 percent rise in gasoline prices between January and mid-July, Announcement 2026-11 raised it to 76 cents a mile effective July 1, 2026. One calendar year, two rates. Almost nothing that a bookkeeper touches knows this. Expense templates hold one number. Spreadsheets hold one number. Ask a chatbot what the 2026 mileage rate is and it will confidently say 72.5 cents, because that is the number the year opened with and the number most of its sources were written against.
Getting the rate wrong is only the first half. The second half is that a mileage reimbursement is not automatically tax-free money. It is tax-free only while the arrangement stays an accountable plan under Treas. Reg. 1.62-2, and that regulation has two hard clocks:
- the employee substantiates the expense within 60 days, and
- any excess over the substantiated amount comes back within 120 days.
Miss the first clock and it is not just the excess that becomes wages. The entire payment becomes wages.
Here is the arithmetic on that ordinary report, run for a trip taken in September 2026:
Business miles 640
Rate reimbursed 72.5 c/mile
Flat car allowance $250.00
IRS rate for Jul 1 - Dec 31, 2026 76.0 c/mile <- Announcement 2026-11
Tax-free ceiling 640 x 0.76 = $486.40
Total actually paid 640 x 0.725 + 250
= $714.00
Above the ceiling = $227.60 -> W-2 wages, not returned in 120 days
Employer payroll tax 7.65% = $17.41
Short of the IRS rate on the miles= $22.40 -> still owed to the employee
Two errors in opposite directions, on one report, in one month. The $250 allowance was never substantiated by miles, so it is excess and it lands on the W-2. And because the miles themselves were paid 3.5 cents under the correct rate, the employee is simultaneously owed $22.40 if the company policy is "we pay the IRS rate."
Now change one field. Say the employee handed the log in 74 days after the trip instead of 21 — a July trip reconciled in late September, which is exactly what a lot of firms are doing right now. The 60-day window is gone, and the ruling changes from "$227.60 is wages" to "the whole $896.80 is wages." Nothing about the receipts changed. Only the calendar did.
The deadline on all of this is January 31, 2027, when Form W-2 is due. Anything you did not catch by then is not a spreadsheet edit any more, it is a Form W-2c, and an incorrect information return carries up to $340 per form under IRC section 6721 and up to $340 again under section 6722 for the copy furnished to the employee.
So we built the check as a browser extension, because that is where the work already happens — in QuickBooks Online, in Expensify, in Ramp, in a Google Sheet. Click the icon, key the seven fields, get the ruling. It picks the rate from the trip date instead of asking you to remember which half of 2026 you are in. It runs the 60-day and 120-day tests. It stops Social Security at the 2026 wage base of $184,500 rather than charging 6.2 percent on wages that are past it, which is why a sales lead at $184,450 year-to-date shows $4.14 of employer tax on $71.75 of excess and not $5.49.
The calculation is free. All of it, in the popup and on the web page, with no key, no usage cap and no watermark on the answer, because a half-answer is worth nothing to someone reconciling forty reports. The $60 full version does one different thing: it writes each check to a .csv audit trail you keep, one row per employee per month, carrying the miles, the rate that was applied and the ruling that followed from it. That is the file your auditor asks for and the file nobody has, because it was never anywhere except in the bookkeeper's head at the moment they keyed the report.
The rate will move again on January 1, 2027. The 60 and 120 day clocks will not.
Free in your browser (the same rules): https://getreadystack.com/tools/mileage-reimbursement-audit-2026
Licence ($60, once, 7-day refund): https://buy.polar.sh/polar_cl_ppCsRdiRBIDkihfqIT5BFEKI3jGtfZyS4xj3T3glEZ2
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