How to Keep a Mileage Log: What Each Trip Must Show

A mileage log is one record among several that describe the same drive. Each one proves something different.

A calendar can corroborate where you were expected to be. A mileage log records where you went, how far, and why. Whether a trip qualifies, and at what rate, is covered in the mileage deduction guide; hours on site are covered in how to track time on a job.

IRS Publication 463, chapter 5, Table 5-1, lists what to prove for car use: the mileage for each business use, the date, the business destination and the business purpose. The other fields make the record easier to check.

Once a year, for each vehicle, keep its total miles for the year and the date it began business use (Table 5-1). Odometer readings at the start and end of the year are the practical way to support the total; Pub. 463's sample log (Table 5-2) records start and stop readings for each trip.

Clamp saves a trip with miles and a purpose, and asks for a destination on a business trip. That is the app's minimum, not the IRS standard.

Log the trip the same day, before the end of the day, while you still know why you drove there. If automatic detection caught it, review it the same day and add what the app can't know: the purpose, the job and the trip type.

A filled example, the trip published in the mileage deduction guide:

Detected, not yet counted

Reviewed with a purpose

A detected drive in Clamp: it waits under Detected trips until you review it, and Review opens it filled in from the detection for you to add the purpose and the job. Demo data; the trip is the worked example.

Clamp records one trip type per entry and can't split a detected drive. If detection captures business and personal legs together, don't confirm the combined drive as business. Discard it and record the business and personal legs by hand as separate trips.

The published trip, at the IRS business rate for its date. The rates are 72.5 cents a mile through June 30, 2026, and 76 cents from July 1 (IRS standard mileage rates; Announcement 2026-11).

Rate by trip date

The logged trip in Clamp, priced at the rate for its own date. Demo data.

On August 18, 2026:

The same trip on June 30, 2026, at 72.5 cents, and on July 1, at 76 cents, as an illustration:

Together, 40.0 miles:

Cross-check: because the two trips are the same 20.0 miles, their average rate is $0.7425; 40.0 × $0.7425 = $29.70.

That is why every trip needs its date: the same 20.0 miles is worth a different amount a day apart. These are standard-rate figures for an eligible trip. Whether a trip is eligible is in the mileage deduction guide.

Made at the time. Pub. 463 asks for records made at or near the time of the business use, and explicitly treats a weekly log covering that week as timely. This guide logs trips the same day, because the purpose and the destination are still fresh.

Written, not remembered. An adequate record is a written one, such as a log or a trip sheet. A computer or app record can serve as the written record, provided it contains the required elements and is adequately supported (Pub. 463, chapter 5, "What are adequate records?").

Backed up where it can be. Calendars, invoices, supplier receipts, job schedules and location history can corroborate a log. Use them to corroborate a timely log rather than as your normal mileage-recording system.

When records are incomplete, Pub. 463 lets you prove a missing element with your own specific statement plus other supporting evidence. For the date, the place and the amount, that evidence generally has to be direct or documentary. The business purpose can sometimes be shown from the circumstances ("What if I have incomplete records?"). A log rebuilt in April from a calendar is weaker than one kept as you went.

Destroyed records are a separate rule. When records are lost to a fire, a flood or another casualty beyond your control, the publication permits a reasonable reconstruction ("Destroyed records"). Forgetting to keep a log is not that.

Sampling. Pub. 463 permits adequate records for a representative part of the year when other evidence shows that part is representative ("Sampling"). This guide logs every trip rather than having to prove a sample period was representative.

The annual vehicle record. For each vehicle, keep its total miles for the year and the date it began business use. Under this guide's practice, read the odometer at the start and end of the year, and when the vehicle starts or stops business use. The rest of the vehicle record (cost, depreciation, the actual-expense method) is in the mileage deduction guide.

Decide these once, so every trip is logged the same way.

To the tax return. The log is the evidence behind the deduction (the mileage deduction guide).

To your accountant. Clamp's accountant export carries business miles as a reference line for review, not as a posted expense.

To the job. A trip linked to a job appears on that job's trip list.

To your prices, not your job cost. Clamp doesn't add logged miles to job cost. In Clamp's pricing, vehicle cost is recovered through the vehicle allocation on each labor role. That is Clamp's pricing design, not an IRS rule.

Michael C. Stone, a builder and remodeler with more than six decades in the industry and the author of Estimating Construction Profitably, treats travel time and mileage as costs an estimate may need to carry (chapter 7, "Estimating Labor", "Travel Time"). His point is that travel cost has to be recovered somewhere, not paid silently out of profit. When a job's travel is unusual, price it in the proposal or a change order (How to Write and Price a Change Order). Don't price it by passing the IRS rate through.

Most mileage records fail for the same few reasons.