IFTA Mileage Records: What Auditors Demand and How Long to Keep Them

You must retain mileage records for exactly 4 years from your IFTA return's due date (not filing date), and auditors will reject summaries, estimates, or incomplete trip sheets—they want start/end odometer, date, route, and per-jurisdiction miles on every trip.

The 4-year retention window starts from the return due date, not when you file

The 4-year clock begins on the return's due date, not the date you actually file. File early in April, late in June, or not at all until a jeopardy notice arrives—the retention period stays the same. Each quarterly return has its own independent due date: Q1 due April 30, Q2 due July 31, Q3 due October 31, Q4 due January 31 of the following year. Your Q1 2026 records don't expire until April 30, 2030. Your Q2 2026 records don't expire until July 31, 2030.

If the base jurisdiction issues a waiver or jeopardy assessment, keep everything longer. IRP carriers must retain mileage records for 5.5 years because apportionment data overlaps multiple years. If you run both programs, save for 5.5 years—don't split the difference.

Paper trip sheets must show odometer, date, origin/destination, route, and miles per state

Every trip sheet needs five things or an auditor will reject it:

1. Starting and ending odometer readings. Not "about 47,000" or a blurry photo. Legible numbers. If your truck has a hub odometer or ECM readout, use that instead.
2. Trip date. Month, day, year. "Early June" doesn't work.
3. Origin and destination. City and state minimum. "Left Dallas, arrived Tulsa" is enough.
4. Route of travel. The highways you took. Not required to be hyper-detailed, but "I-20 to I-44" matters if you're claiming miles in multiple states.
5. Miles per jurisdiction during that trip. If you run 400 miles with 240 in Texas and 160 in Oklahoma, write both numbers. Monthly or quarterly summaries alone will be rejected—auditors need the daily source document.

Handwritten logs are the audit standard because they're harder to fabricate than a spreadsheet created in hindsight. Photocopies are acceptable; originals don't need to be kept in physical form.

GPS data is acceptable only if it records a point every 10 minutes with 4-decimal latitude/longitude

If you use a vehicle tracking system instead of hand logs, the system must create a record at least every 10 minutes while the engine is running: timestamp, latitude to 4 decimal places (0.0001 degrees), and longitude to 4 decimal places. That precision is roughly 36 feet. If your system records every 30 minutes or doesn't store coordinates to that decimal precision, it fails IFTA audit.

The data must be exportable to XLS, XLSX, CSV, or delimited text—PDF, JPEG, PNG, or Word formats are rejected. A PDF map screenshot is not an audit record. There is no vendor certification for IFTA, despite what some software companies claim. Many ELD systems don't meet these standards because they only retain 6 months of data. Verify your system meets Iowa DOT P530 standards before relying on it for IFTA.

Raw GPS files must be retained for 4 years, not just summarized distance reports. If your vendor deletes raw data after 90 days and keeps only monthly summaries, that's not compliant.

Worked example: A driver's Q2 trip sheet audit with mixed paper and GPS records

Driver runs Q2 2026 (April–June) across four states: 5,400 total miles and 750 total gallons purchased.

Driver's claimed fleet MPG: 750 gallons ÷ 5,400 miles = 7.2 MPG.

Auditor samples week 3 of records (June 8–14). Trip sheets for three days are illegible—pen is smudged, mileage totals unreadable. GPS archive for that week is missing from the driver's file. Auditor cannot verify 280 miles claimed for that week.

Missing or illegible records in any week triggers reassessment. Auditor recalculates the driver's MPG for the entire quarter down to 4.0 MPG (the IFTA penalty floor). New calculation: 5,400 miles ÷ 4.0 MPG = 1,350 gallons (not 750). The difference is 600 gallons of "unaccounted fuel." At an average IFTA rate of $0.195 per gallon across those four states, that's an additional assessment of roughly $117. Add penalties and interest, and the driver owes $200+ more than reported—on top of the original $147.70 tax liability.

One driver's failed records can trigger fleet-wide reassessment. If that driver is one of ten in your operation and the auditor finds similar gaps in others' logs, the penalty applies to all of them.

Fuel receipts must match vehicle, gallons, date, and seller

Every receipt must show date of purchase (month, day, year), seller name (truck stop, gas station, fleet card company), fuel type (diesel, gasoline, biodiesel blend), gallons or liters purchased (specific quantity), and which unit was fueled (truck number, trailer ID, or equipment ID if bulk).

Altered, erased, or illegible receipts are rejected unless you can prove validity through a second source (credit card statement matching the amount and date, for example). Prepaid receipts showing only "Pilot Flying J Prepaid $200" with no pump details don't qualify. Generic credit card statements without itemized pump data don't qualify either. You need the actual pump receipt or a fleet card statement that breaks down gallons and per-transaction fuel type.

Photocopies and scanned images are acceptable. Originals don't need to be kept in physical form—digital archives of receipt PDFs are audit-grade records.

Bulk storage tanks require delivery receipts, reconciliation, tank specs, and withdrawal logs

Bulk fuel is a separate audit track. Delivery receipts for every fuel delivery to the tank are required. Quarterly inventory reconciliation is mandatory: how much fuel came in, how much went out, what's left. Do this for each tank at end of Q1, Q2, Q3, Q4. You also need tank capacity specs (gallons or liters the tank holds) and withdrawal logs for every pull from the tank, showing tank location, date of withdrawal, quantity withdrawn, fuel type, and vehicle or equipment ID that received the fuel.

If delivery receipts total 2,000 gallons for the quarter, withdrawal logs total 1,950 gallons, and you claim 1,950 gallons on your IFTA return, you're fine (50 gallons is shrinkage/evaporation). If delivery receipts total 2,000 gallons and you claim 2,000 gallons but withdrawal logs only show 1,200 gallons going into vehicles, the auditor assesses you for 800 unaccounted gallons at the highest IFTA rate in your jurisdiction. Shortage between receipts and withdrawals triggers fuel-tax assessment on the missing gallons.

Auditors penalize inadequate records by recalculating your MPG down to 4.0 or cutting claimed efficiency by 20 percent

If your submitted records fail IFTA standards for even one vehicle in your fleet, the auditor can apply the penalty to all vehicles in that quarter. You don't have to have zero records—gaps, illegible entries, or summaries without source documents trigger reassessment.

Assessments for bad records can exceed $10,000 per vehicle. The 4.0 MPG floor (or 1.70 KPL for metric) or 20% reduction is applied retroactively to all quarters in the audit period. A 4-quarter audit with six vehicles and incomplete records in two vehicles means six vehicles × four quarters × potential $2,500+ per vehicle penalty. It adds fast.

Missing receipts, gaps in mileage logs, or illegible trip sheets trigger this penalty. One week without trip sheets in a 13-week quarter gives the auditor justification to recalculate the entire quarter.

Organize records by quarter, unit, and jurisdiction; don't rely on one person's email or unsupported spreadsheets

Auditors expect to pull any quarter's fuel and mileage data in under 10 minutes. One spreadsheet owned by one dispatcher is a liability when that person leaves. If your company depends on Danny in dispatch, and Danny's the only one who knows where the Q3 2024 receipts are, you fail the audit.

Digital archives (PDF scans of receipts indexed by date, unit, and quarter) are acceptable. Cloud storage with audit trails is safer than paper boxes in a garage. When the auditor shows up, you should be able to get to Q2 2025 records in five minutes flat.

If you switch record-keeping systems mid-year, keep both old and new accessible for the audit period. Don't assume your new software pulled all the data correctly from your old system. Spot-check a few months to verify.