IFTA audit: how your fuel tax reports get checked
Filing the quarterly return is not the end of it. Years later, your base jurisdiction can test every quarter against your own mileage and fuel records, for every state you ran in.
The IFTA audit in numbers
An IFTA audit is your base jurisdiction checking your quarterly fuel tax reports against your own mileage and fuel records, on behalf of every IFTA member. Expect about 30 days' notice, a sample of your trips and receipts, and a report that bills or credits each jurisdiction. You get at least 30 days to appeal.
Most carriers treat the quarterly fuel tax report as the finish line. For your base jurisdiction it is a claim to be checked, and the IFTA audit is where that happens, quarter by quarter, sometimes years after you filed.
This guide covers what happens after you file: how accounts are picked, what the auditor does, what can change, and how to appeal. Preparing the return itself is in our IFTA quarterly filing guide, and the federal fuel tax credit, a separate thing entirely, is in our trucking fuel tax guide.
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Key takeaways
One audit speaks for every jurisdiction
Your base jurisdiction audits you on behalf of all IFTA members, and its findings become final for all of them once the appeal window closes.
Selection is partly a quota
Each base jurisdiction must audit an average of 3% of its accounts a year, including set shares of its lowest- and highest-mileage accounts.
Missing receipts cost credits, not gallons
A bad receipt loses its tax-paid credit, but the auditor can cut your total fuel only with clear proof from your own records.
Weak records cost the most
If your records are inadequate for the whole fleet, your fleet MPG is cut by 20% or set at 4.00, which raises taxable gallons everywhere.
The appeal clock is short
You get at least 30 calendar days from the final audit report to appeal in writing. After that, the findings stand.
In this articleContents
What is an IFTA audit?
An IFTA audit is your base jurisdiction's examination of the fuel tax reports you filed and the distance and fuel records behind them. Under the IFTA Articles of Agreement (R1310), the base jurisdiction audits its licensees on behalf of every member jurisdiction, so one audit settles what you owe all of them.
Other jurisdictions keep the right to audit you as well, at their own expense, and can join your base jurisdiction in a joint audit that it directs (R1350). Once the appeal and re-examination windows close, the findings are final for you and every member, except in cases of fraud (P510).
Is a records review the same as an audit?
No. Since 2023, a base jurisdiction may run a records review: an evaluation of your record-keeping system and internal controls, meant to educate. It cannot produce a tax assessment, and once it is complete you can't be audited for 180 days, so you have time to fix what it found (Audit Manual A500, A510).
Use that time. When a review finds noncompliant records, IFTA's guidance is for the jurisdiction to instruct you to file amended returns for quarters already filed.
How are carriers picked for an IFTA audit?
Part of IFTA audit selection is a quota. Each base jurisdiction must audit an average of 3% of its IFTA accounts per year over a five-year compliance review period, not counting new licensees (A250). An audit counts only if it covers a full license year or at least four consecutive quarters.
The quota has to reach both ends of the fleet list (A260):
- Low-distance accounts: at least 15% of the required audits, drawn from the 25% of licensees that reported the fewest miles the year before
- High-distance accounts: at least 25% of the required audits, drawn from the 25% that reported the most miles
- Any other account: the rest, where records reviews can stand in for up to a quarter of the required audits, at three reviews per audit
Beyond that, IFTA does not publish selection triggers, and each jurisdiction picks its own. What the Audit Manual does require is that the auditor analyze your returns and note unusual trends or variances before the audit starts (A310). So make every quarter explainable: if your fleet MPG moves sharply from one quarter to the next, know why before anyone asks.
What happens during an IFTA audit?
An IFTA audit follows a set sequence in the Audit Manual, with your base jurisdiction's law filling in the details.
Step 1: You get notice
The jurisdiction should contact you at least 30 days before the audit and tell you the audit period, the records it will examine, and the proposed start date. It can start sooner if you agree, or for just cause (A420).
Step 2: You produce the records
The auditor requests the records for the audit period: distance records, fuel receipts, bulk tank records, and monthly summaries of each vehicle's miles and fuel by jurisdiction (A430, P560). Any format works if the jurisdiction can audit it. If your miles come from GPS, the data rules are in our guide to ELD data for IFTA.
Where you keep the records matters. If they are outside your base jurisdiction and its auditors travel to them, you may have to pay their reasonable per diem and travel costs (P510).
Step 3: The opening conference
The auditor should meet with you to go over your operations, how you account for distance and fuel, the records to be examined, and the sample period (A440).
Step 4: Controls testing and sampling
Most audits run on a sample. The auditor describes your distance and fuel systems, compares your summaries with your returns, and tests your internal controls; the more reliable the controls, the less the sample has to cover (A320, A330). Findings from the sample are then projected across the audit period.
If your jurisdiction uses distance software, the auditor must use it to verify the miles you reported (A330).
Step 5: Closing conference and report
At a closing conference, the auditor should walk you through any noncompliance and what to improve (A450). The written report then goes to you and to every jurisdiction where you reported, or should have reported, miles or fuel, with a billing summary by quarter and jurisdiction (A460, R1370). You can ask for the schedules and worksheets behind the findings.
What can an IFTA audit change on your returns?
An IFTA audit can change your miles, your fuel economy, and your tax-paid credits, and each change flows through to every jurisdiction on the return. It can also show that you overpaid.
| Finding | What the auditor can do | Rule |
|---|---|---|
| Records adequate for the fleet | Adjust your reported fleet MPG to what the records support | A350 |
| Some vehicles' records missing or badly impaired | Rebuild those vehicles' miles and fuel from your history, similar vehicles, industry averages, or third-party fuel records | A350 |
| No basis to rebuild those vehicles | Cut their MPG by 20% or set it at 4.00 | A350 |
| Records inadequate for the whole fleet, or none produced | Cut the fleet MPG by 20% or set it at 4.00 | P570 |
| Receipt missing, altered, or incomplete | Deny the tax-paid credit for that purchase | P550 |
| Miles with no record of where they were driven | Allocate them to jurisdictions by a rational, unbiased method | A340 |
One rule works in your favor: a missing receipt costs you the credit, not the gallons. The auditor can reduce your total fuel only with clear proof from your own records (A360). A lower MPG works the other way, raising taxable gallons in every jurisdiction at once. The record rules behind it are in our guide to filing your quarterly IFTA return.
What about interest and penalties?
Audit interest runs monthly on the running balance you owe each jurisdiction, at two percentage points above the IRS underpayment rate for U.S.-based fleets. An overpayment to one jurisdiction does not reduce the interest owed to another (R1230). A penalty of $50 or 10% of the delinquent tax, whichever is greater, can apply to an underpayment (R1220).
A credit the audit finds isn't refunded while you owe tax, penalty, or interest to any member jurisdiction, unless that amount is under appeal (R1100, R1140).
How do you appeal IFTA audit findings?
You appeal IFTA audit findings in writing to your base jurisdiction, which must give you at least 30 calendar days from when you are notified of the findings (R1390). The clock starts on the date the jurisdiction provides the final audit report (R1370).
The appeal follows your base jurisdiction's administrative procedures. Where it has none of its own, IFTA's default applies: a written hearing request within 30 days, at least 20 days' notice of the hearing, and the right to bring counsel, witnesses, and documents (R1410 to R1430). The base jurisdiction argues the case for the other jurisdictions.
If you still disagree after that, you can ask any member jurisdiction to audit its own share of your operations, and each may accept or refuse (R1450). Separately, other jurisdictions have 45 days from receiving the audit report to give notice that they will re-examine it (R1360).
Don't let the deadline pass quietly. If a delinquency stays unpaid and you file no written appeal within 30 days of the notice, a revocation notice for your IFTA license follows (R1270).
How do you keep fuel tax reports audit-ready?
Keep fuel tax reports audit-ready by building the auditor's checks into your quarterly routine. In an IFTA audit the burden of proof is on you, and the audit is completed with the best information the jurisdiction has (P520).
- Summarize monthly by truck. Total each vehicle's miles and fuel by jurisdiction every month. Auditors can demand these summaries (P560).
- Reconcile before you file. Make sure the summaries add up to the return, because comparing the two is one of the auditor's first steps (A320).
- Use one cut-off. Distance and fuel must close on the same dates every quarter (P540, P550).
- Check every receipt. Date, seller, gallons, fuel type, price, unit number, and purchaser. A fuel card transaction listing from a third party is accepted (P550).
- Close the trip gaps. Each trip's starting odometer should match the last trip's ending reading. Our CDL trip report guide lists what every trip record needs.
- Reconcile bulk tanks. Keep delivery receipts, withdrawal records, and a quarterly inventory reconciliation for each tank (P550).
- Keep four years. Hold records for four years after each return was due or filed, whichever is later (P510).
- Amend instead of waiting. When you find an error in a filed quarter, ask your base jurisdiction how to amend it before an auditor finds it.
If preparing returns every quarter is more than your office can carry, our trucker tax team can prepare and file them from your records.
How Simplex helps you stay ready for an IFTA audit
An audit tests the records behind every return you filed. We help with the returns, the license, and the data they start from.
Quarterly IFTA returns
Our trucker tax team prepares and files your IFTA returns from your mileage and fuel records, and keeps track of your fuel receipts.
IFTA license and decals
Our IFTA permits team files the license application with your base jurisdiction and helps keep the license active.
Mileage data from the cab
Simplex ELD includes fuel usage and IFTA mileage reports in its web portal, next to driver logs and vehicle management.
Frequently asked questions
How far back can an IFTA audit go?+
What triggers an IFTA audit?+
What happens if I fail an IFTA audit?+
How long do I have to appeal an IFTA audit?+
Is a fuel taxes report the same as the federal fuel tax credit?+
Where this information comes from
The rules below come from IFTA's governing documents and the IRS, checked on October 20, 2026. Your base jurisdiction's own law adds to them.
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1
IFTA, Inc. — Articles of Agreement (August 26, 2026 edition)
Who audits (R1310), joint audits and re-examinations, audit reports, appeals (R1390, R1400), penalties, interest, refunds, and revocation.
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2
IFTA, Inc. — Audit Manual (August 26, 2026 edition)
The 3% audit requirement, low- and high-distance selection, notice, sampling, audit adjustments, the audit report, and records reviews.
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3
IFTA, Inc. — Procedures Manual (August 26, 2026 edition)
Record retention and travel costs (P510), burden of proof, distance and fuel records, summaries, and the inadequate records assessment (P570).
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4
IRS — Fuel Tax Credit
What the federal Fuel Tax Credit covers, Form 4136, and that it does not apply to regular driving.
Written by
Simplex Group
Permits & Fuel Tax Team, Simplex Group
Reviewed for technical accuracy by a Simplex permitting manager before publication. Simplex has registered and filed permits and fuel taxes for interstate carriers across all 50 states for more than 20 years.
Published · Updated
Related articles and services
The best IFTA audit is one your records already answered
An auditor tests what you filed against what you kept. Monthly summaries, one cut-off, complete receipts, and four years of files turn an audit into a review instead of a rebuild.
If you want help getting your fuel tax records and quarterly returns in that shape, talk to our team.