What Happens in an IFTA Audit: What They Check, What You Need, and How to Be Ready
What Happens in an IFTA Audit: What They Check, What You Need, and How to Be Ready
Sooner or later, it happens. A letter shows up from your base state telling you your IFTA records are going to be looked at. You have not done anything wrong — they just picked your name.
This guide walks you through the whole thing: how audits work, what they look for, what records you must have, and what to do if they say you owe more. Every fact below comes from IFTA Inc, state Department of Transportation pages, and state comptroller offices. No guesswork.
How Often Do Audits Happen?
Every base state must audit an average of 3% of its IFTA accounts each year. That is not a cap — it is a floor. Your state can audit more if it wants.
Of those audits:
- At least 15% must be low-mile accounts
- At least 25% must be high-mile accounts
- The other 60% can be any size
Source: IFTA Audit Manual — audit selection standards
If you run a small fleet with low miles, you are not safe. The 15% rule means they must look at small operators too.
How Will You Find Out?
Your base state will send you a written notice — by mail, email, or phone — before the audit starts.
In Minnesota, the Department of Public Safety gives 30 days' notice before the audit begins.
In South Carolina, the DMV says audits happen "during normal business hours and, to the extent possible, notification will be given in advance."
The exact lead time depends on your base state. But you will know before they start — it will not be a surprise knock on your door.
Most audits are done by mail or online. The Minnesota DVS notes that "the majority of the audits are completed by mail or electronically." You send in your records, they check the numbers, and they send back their findings.
How Far Back Do They Look?
An IFTA audit must cover at least four (4) back-to-back quarters — a full year of returns.
Source: IFTA Audit Manual — "Such audits shall cover all of the returns that were filed or required to be filed during a license year or shall cover at least four (4) consecutive quarters."
That means every receipt, every trip log, every odometer reading for a full year must be at hand.
What Records Must You Keep?
The auditor will ask for two stacks of records: distance and fuel. Here is exactly what each must hold.
Distance Records
For every trip, you need:
| Field | What It Means |
|---|---|
| Start and end dates | The day the trip began and ended |
| Origin and destination | City and state where you started and where you stopped |
| Route of travel | The path you took |
| Odometer readings | Beginning and ending numbers from odometer, hubodometer, or ECM |
| Total trip miles | The full length of the trip |
| Miles in each state or province | How far you drove in each one |
| Truck unit number | Which truck made the trip |
Source: CDTFA — Getting Started with IFTA | Iowa DOT — IFTA Record Keeping
Fuel Records
For every fill-up, you need:
| Field | What It Means |
|---|---|
| Date | When you bought the fuel |
| Seller name and address | The truck stop or station — name and street address |
| Gallons | How much fuel went in the tank |
| Fuel type | Diesel, gasoline, propane, CNG, etc. |
| Price per gallon or total cost | What you paid |
| Truck unit number | Which truck got the fuel |
| Buyer name | Must be your company name, not the driver's name |
Source: Iowa DOT — IFTA Record Keeping | CDTFA — Getting Started with IFTA
Fuel card slips alone are not enough. The Texas Comptroller FAQ warns: "It is an audit issue if the fuel card receipts do not identify the vehicle into which the fuel is delivered." Your card receipt must show which truck got the fuel.
Bulk Fuel Records
If you keep fuel in a tank at your yard and fill your trucks yourself, you need more:
- Receipts for every delivery into the tank
- Quarterly stock counts for each tank
- The size of each tank
- Withdrawal logs showing date, gallons, fuel type, and truck unit number
Source: Iowa DOT — IFTA Record Keeping
GPS and ELD Records
If you use GPS or an ELD to track miles, the data must meet these standards:
- A reading at least every 10 minutes when the engine is running
- Date and time of each reading
- Latitude and longitude with at least 4 decimal places (0.0001)
- Odometer reading from the engine control module (ECM)
- Truck unit number
The data must be saved in a spreadsheet format — XLS, XLSX, CSV, or a text file with clear columns. PDF screenshots, JPEGs, PNGs, and Word docs are not good enough.
Source: Minnesota DVS — Audit Record Keeping | Iowa DOT — IFTA Record Keeping
What Are Gap Miles — and Why Do They Matter?
Gap miles are the holes in your trip logs.
Say your odometer went up by 12,000 miles this quarter, but when you add up all the state-by-state miles from your trip logs, they only come to 10,000. Those missing 2,000 miles are gap miles.
The Texas Comptroller FAQ puts it plainly: "Gap miles are the difference in the miles recorded for a trip on your trip sheet and the actual miles traveled based on the beginning and ending odometer or hubmeter readings for that trip. Gap miles are usually an audit issue."
Gap miles tell the auditor that you drove somewhere but did not log it. They will want to know where those miles went — and if tax should have been paid on them.
How the Auditor Checks Your Math
Here is what the auditor does with your records:
1. They add up your total miles from your trip logs and odometer readings.
2. They add up your total gallons from your fuel slips.
3. They work out your fleet MPG — Total Miles ÷ Total Gallons.
4. They check if the MPG makes sense. A loaded Class 8 diesel truck should land somewhere between 5.0 and 7.5 MPG. If yours says 11, they know something is off — either your miles are too high or your gallons are too low.
5. They break down miles by state and work out how many taxable gallons each state should get — the same way you did on your return.
6. They compare their numbers to yours. If there is a gap, you owe the difference plus interest.
The auditor's job is to see if what you filed matches what your records show. If your records are clean and your math is right, the audit ends with no changes.
What Happens If They Find You Owe More?
If the auditor's numbers come out higher than what you filed, they will send you an assessment — a bill for the extra tax, plus interest.
Interest for 2026 runs at 9% per year (0.75% per month), starting from the day after the original due date of the return.
Source: IFTA Inc — Interest Rates
If your records are missing or too sloppy to check, the cost can be steep. The Minnesota DVS warns that "assessments for inadequate or unavailable records may exceed $10,000 per vehicle."
Your Rights During an Audit
You are not without a say. The Minnesota DVS lists these carrier rights:
- Know why they are asking. You have the right to know why the state wants your records.
- Get clear answers. You can ask questions and get a straight reply.
- See the findings. The auditor must show you what they found and explain any changes.
- Keep things private. Your records and tax details are kept in confidence.
- Bring someone with you. You can have a CPA, bookkeeper, or anyone else sit in or speak on your behalf.
How to Fight Back: The Appeal
If you think the audit got it wrong, you can push back.
In Minnesota, you must file your appeal within 30 days of the audit-finding bill, in writing, with your backup paperwork and your reasons.
Source: Minnesota DVS — Audit Procedures
In South Carolina, you may "appeal any action or audit finding by submitting a written request for an administrative hearing within 30 days of receipt of the original notice of assessment."
Source: South Carolina DMV — IRP and IFTA Audits
The window to fight is short — 30 days in most states. If you miss it, the bill stands.
How Long Must You Keep Records?
The baseline is four years from the due date of the return or the date you filed it — whichever comes later.
Source: Texas Comptroller — Fuels Tax FAQ | CDTFA — Getting Started with IFTA
State-specific warning — South Carolina requires five years. The South Carolina DMV states: "Under the provisions of IFTA and IRP, operations records must be maintained for five years." If you run miles through South Carolina, keep your records for the longer stretch.
Some other states may also have longer windows. Check with your base state to be sure.
California's Free Records Check
If you are based in California or hold a California IFTA license, the CDTFA runs a free Records Review Program.
This is not an audit. It is a check-up.
- Who can sign up: Any licensee who started within the last 12 months gets one by default. Anyone else can ask for one.
- What they look at: Your distance and fuel tracking system, your slips and trip logs, and the summaries you use to fill out your returns.
- How long it takes: About 4 hours, if your records are laid out and ready.
- Can it hurt you? No. "The records review does not compare your records to your quarterly tax return to determine adjustments and cannot result in a tax assessment."
- What you get back: A two-part letter — one part tells you what looked good, the other tells you where to tighten up.
- Bonus: After a records review, you will not be picked for an audit for at least six months.
Source: CDTFA — Industry Topics
If you are a California licensee, this is worth doing. It is free, it cannot cost you money, and it gives you a six-month shield from audits.
Common Red Flags That Get You Picked
While some audits are picked at random, these things draw the eye:
- MPG that looks too good. A Class 8 reporting 10+ MPG on diesel will get a second look.
- Gap miles. Your odometer says one thing, your trip logs say another. (Texas Comptroller FAQ)
- Fuel slips without a truck number. If the receipt does not name the truck that got the fuel, it is a problem. (Texas Comptroller FAQ)
- Round numbers on every line. Real trips do not come out to 1,000.0 miles each.
- Missing quarters. Filing three out of four quarters is a flag.
- Big swings quarter to quarter. Q1 shows 40,000 miles, Q2 shows 5,000, with no clear reason.
Audit-Ready Checklist
Use this list to stay ready at all times — not just when the letter comes:
- Every trip logged with dates, origin, destination, odometer start and end, miles by state, truck unit number
- Every fuel stop logged with date, station name and address, gallons, fuel type, price, truck unit number
- Buyer name on fuel slips is your company name (not the driver's name)
- Fuel card slips show which truck got the fuel
- No gap miles — trip log miles match odometer readings
- GPS/ELD data saved as XLS, XLSX, or CSV (not PDF or screenshots)
- GPS/ELD logs show readings every 10 minutes with lat/long to 4 decimal places
- Bulk fuel tanks have withdrawal logs and quarterly stock counts
- Monthly fleet summaries done (miles and gallons by truck)
- Records kept for at least 4 years (5 years if you run through South Carolina)
- Zero-mile quarters filed on time
How WheelsAndAxle Keeps You Audit-Ready
WheelsAndAxle was built to take the sweat out of record keeping — so that if the audit letter ever shows up, you hand over clean records and move on.
Every fuel stop logged with date, state, gallons, fuel type, and truck unit — right from your phone.
Every trip logged with origin, destination, and miles by state — no more scribbled trip sheets.
Monthly and quarterly summaries built as you go — not thrown together the night before a deadline.
Your records stored in one spot for as long as your account is active — not in a shoebox, not on a lost thumb drive.
When the auditor asks for your Q3 2025 distance and fuel records, you pull them up in seconds.
$1.99/month. That is the cost of being ready.
Important Notice
WheelsAndAxle is a record-keeping and preparation tool — not a tax advisor, CPA, or filing service. We help you build clean records and IFTA worksheets, but you are the one who files and you are the one who stands behind every number. Always check your figures against the IFTA Tax Rate Matrix and your base state's filing system before you submit. If you get an audit notice and are not sure what to do, talk to a CPA or tax professional who knows fuel tax.
We do not file returns on your behalf. We do not give tax advice. We give you the tools to keep your records straight — but the last word is always yours.
Official Sources
Every fact in this guide comes from one of these:
- IFTA Inc — Carrier Information
- IFTA Audit Manual (2026)
- IFTA Interest Rates
- IFTA Tax Rate Matrix
- California CDTFA — Getting Started with IFTA
- California CDTFA — Industry Topics (Records Review Program)
- Texas Comptroller — Fuels Tax FAQ
- Iowa DOT — IFTA Record Keeping Requirements
- Minnesota DVS — Audit Procedures
- Minnesota DVS — Audit Record Keeping Requirements
- South Carolina DMV — IRP and IFTA Audits
This guide is for informational use only. WheelsAndAxle generates IFTA preparation worksheets — not filed returns. We are not a CPA, tax advisor, or filing service. You bear sole responsibility for the accuracy of your IFTA records and returns, and for checking all figures with your base jurisdiction before filing. When in doubt, talk to a qualified tax professional.
Disclaimer: WheelsAndAxle generates IFTA worksheets as preparation aids only. We are not a tax advisor, CPA, or filing service. Users bear sole responsibility for verifying all figures with their base jurisdiction before filing.
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