Mileage Log Requirements for IRS: What to Record and How to Store It

Most people search for IRS mileage log requirements after months of missing notes — or worse, after getting a notice from the IRS. The right time to fix your logging workflow is now, while your records are still recoverable.

This guide covers what the IRS actually requires, the legal basis behind those requirements, how long to keep records, what happens if you are audited without a log, and how digital tools compare to paper.

The legal foundation: IRC Section 274(d)

The mileage log requirement is not just an IRS suggestion. It comes from Internal Revenue Code Section 274(d), which imposes “adequate records” or “sufficient evidence” requirements for certain deductions, including vehicle expenses.

Under Section 274(d), you must substantiate four elements for each business use of a vehicle:

1. Amount — the number of miles driven for business
2. Time — the date of each trip
3. Place — the destination or route
4. Business purpose — why the trip was necessary

Without adequate records covering all four elements, the IRS can disallow the entire vehicle expense deduction — not just reduce it.

IRS Publication 463: Travel, Gift, and Car Expenses provides the detailed guidance on how to meet these requirements. Chapter 5 of Pub 463 specifically addresses recordkeeping.

What your mileage log must contain

For each business trip, your log needs these fields:

• Date of the trip (not just the month — the specific date)
• Destination — the address, client name, or enough route context to identify where you went
• Business purpose — “client meeting,” “job site inspection,” “supply pickup” — a brief phrase that explains why the trip was business-related
• Miles driven — odometer readings (start and end) or GPS-tracked distance

You should also record your odometer reading on January 1 and December 31 of each tax year. This establishes your total annual mileage, which the IRS uses to verify your business-use percentage.

Optional but recommended fields

• Vehicle identifier — necessary if you use more than one vehicle for business
• Project or client tag — useful for per-project cost allocation
• Parking and toll receipts — deductible on top of the standard mileage rate
• Trip classification — business, commute, personal, medical, charity

The “contemporaneous” standard

Publication 463 states that records made at or near the time of the expense have “more value than a statement prepared later.” The IRS does not define an exact deadline, but courts have consistently held that logs created weeks or months after the fact carry less weight than those recorded the same day or same week.

In practice, this means:

• Recording trip details within one to two days is strong
• Weekly review and annotation is acceptable
• Reconstructing six months of trips from memory at tax time is weak evidence that courts and the IRS frequently reject

How long to keep mileage records

The IRS record retention rules apply to all supporting documents, including mileage logs.

Standard retention: 3 years

The general rule under IRC Section 6501(a) is that the IRS has 3 years from the date you file your return to assess additional tax. Keep all mileage records for at least this long. If you file your 2026 return on April 15, 2027, retain records through at least April 15, 2030.

Extended retention: 6 years

Under IRC Section 6501(e), if you underreport your gross income by more than 25%, the IRS has 6 years to assess additional tax. If there is any chance your income reporting is complex or variable — common for contractors with multiple revenue streams — keeping records for six years is the safer choice.

Fraud or failure to file: no limit

If the IRS alleges fraud or you fail to file a return, there is no statute of limitations. Records can be requested at any time.

Practical recommendation

Keep mileage logs for at least 6 years from the filing date. Digital storage makes this trivially cheap. There is no downside to retaining records longer than the minimum.

What happens if you are audited without a log

If the IRS selects your return for examination and you cannot produce adequate mileage records, the outcome depends on what evidence you do have.

Complete disallowance

The default outcome under Section 274(d) is that the deduction is disallowed entirely. Unlike most deductions, where the IRS might accept partial substantiation, vehicle expenses under 274(d) face an all-or-nothing standard for the substantiation elements.

The Cohan rule: a limited safety net

The Cohan rule (from Cohan v. Commissioner, 1930) allows taxpayers to claim estimated deductions when they can demonstrate that an expense was incurred but cannot prove the exact amount. Under Cohan, the court may allow a reasonable estimate.

However, there is a critical limitation: the Cohan rule does not apply to expenses governed by Section 274(d). Congress specifically enacted the strict substantiation requirements of Section 274(d) to override Cohan for vehicle expenses, travel, and entertainment. Courts have repeatedly confirmed this — see Sanford v. Commissioner, T.C. Memo 2006-46, among others.

In practice, this means:

• If you have some records but gaps, you may keep deductions for the documented trips
• If you have no contemporaneous records at all, the entire vehicle deduction is at risk
• Reconstructed logs created after an audit notice carry almost no weight

The safest approach is to never rely on the Cohan rule for mileage. Maintain contemporaneous records throughout the year.

Penalties on top of disallowance

Beyond losing the deduction, you may owe:

• Accuracy-related penalty — 20% of the underpayment under IRC Section 6662
• Interest — accruing from the original due date of the return
• In extreme cases, fraud penalties — 75% of the underpayment

Digital vs. paper logs: what the IRS accepts

The IRS does not require paper logs. Publication 463 states that electronic records are acceptable as long as they are accurate, complete, and retrievable. Revenue Procedure 98-25 provides additional guidance on electronic recordkeeping requirements.

Paper logs

• Work fine for low-volume drivers (a few trips per week)
• Risk: physical damage, loss, illegible handwriting
• Harder to search, sort, or total at filing time

Digital logs (apps and spreadsheets)

• Better for high-volume drivers (multiple trips per day)
• GPS-based apps create automatic, timestamped records — strong contemporaneous evidence
• Easy to export, back up, and search
• Risk: if the app shuts down or you lose access, you lose your records — always export monthly

What makes a digital log IRS-compliant

Your digital records must meet the same substantiation requirements as paper:

1. Each trip has a date, destination, purpose, and distance
2. Records are made at or near the time of the trip
3. You can produce the records on request (export to PDF or CSV)
4. Records are stored for the required retention period

A GPS-based mileage tracker that auto-records trips and lets you add purpose notes satisfies all four requirements — as long as you actually review and annotate the trips.

A simple storage model that scales

Create one folder per tax year, then one subfolder per month:

• tax/2026/01-january/
• tax/2026/02-february/

Inside each month:

• Summary export (PDF)
• Raw log export (CSV)
• Related receipts (parking, tolls) if any

Back up this folder to cloud storage. If you ever need to produce records, you can hand over a clean, organized package instead of scrambling through emails and screenshots.

Weekly and monthly review cadence

Weekly (15 minutes)

• Classify uncategorized trips as business or personal
• Add purpose notes where the destination alone does not explain the business reason
• Fix obvious route mistakes (GPS drift, phantom trips)

Monthly (30 minutes)

• Freeze the month — no more edits after close
• Export summary + raw data to your tax folder
• Verify totals match your work calendar or client invoices
• Record any notes about unusual trips (one-time job site, conference travel)

The log quality you build monthly is what protects your deduction if questions arise two or three years later.

Common failure patterns

Missing purpose text

Trips with no business context are the first thing an examiner questions. A log that shows “14.2 miles” with no purpose note is barely better than no log at all.

Reconstructed logs

Creating six months of trip records from memory introduces errors: wrong dates, missing destinations, inflated mileage. Courts consistently give reconstructed logs little weight. In Noz v. Commissioner (T.C. Memo 2012-272), the Tax Court rejected a mileage deduction where the taxpayer created logs after receiving an audit notice.

Mixed personal and business chains

A 45-mile drive that includes a client visit, a grocery stop, and a school pickup is not 45 deductible miles. Split multi-stop drives into deductible and non-deductible segments. Log each segment separately.

No year-start/year-end odometer readings

Without January 1 and December 31 odometer readings, you cannot prove total annual mileage or your business-use percentage. The IRS specifically asks for these numbers on Schedule C. Set a calendar reminder.

Quick self-audit checklist

Before you file, verify:

• No uncategorized business months
• Every month has archived exports (PDF + CSV)
• Sampled trips include clear purpose and destination context
• Annual business miles total reconciles with monthly export totals
• January 1 and December 31 odometer readings recorded
• Records stored in a location you can access for at least 6 years

A clean log is not just compliance. It is the difference between a confident filing and a defensive one.

If you also need a contractor-specific filing workflow, read Independent Contractor Mileage for Taxes: End-to-End Claim Workflow.

For current rate application, use IRS Mileage Rate 2026: Practical Guide for Self-Employed Drivers.

MileTrack captures trips automatically, classifies them as business, commute, or private, and exports tax-ready reports with all the fields the IRS requires. See the current US product page at miletrack.app/en-us.

Tax note: this article is educational and does not replace advice from a licensed tax professional.