A Fuel Surcharge Audit Checklist: 6 Checks Per Invoice

A fuel surcharge audit checklist has to fit on one screen or nobody runs it. Here are the six checks, in the order that finds the most money fastest: the index series named, the applicable week, the peg and MPG divisor, the base the surcharge is applied to, whether fuel is riding on charges it should not touch, and the arithmetic itself. Each one takes under a minute once you have the contract open, and each one catches a distinct error.

The fuel surcharge is usually the second largest number on a truckload invoice and one of the largest on an LTL bill. It is also the only line that recomputes against a published government number, which makes it the most auditable charge in freight and the one almost nobody audits. Detention needs evidence. Accessorials need argument. Fuel needs a lookup table and a calculator.

Have three things open: the invoice, the carrier contract or rate confirmation, and the EIA weekly on-highway diesel series. Without the fuel clause in front of you, you are guessing rather than auditing.

The checklist at a glance

Work them in order. One through three establish the inputs, four and five establish the base, and six is where you find out whether the carrier’s system did what its own contract says.

Check 1: Which index series does the contract name

EIA publishes on-highway diesel nationally and by PADD region, plus separate series for California and for the West Coast excluding California. All are legitimately “the DOE index,” and they are not close to each other. For the week ending July 27, 2026, EIA reported a U.S. average of $5.313 per gallon, Gulf Coast (PADD 3) at $5.087, and California at $6.670. That is a spread of more than $1.58 per gallon between two published numbers from the same release, worth roughly $163 on a 620-mile load at a 6.0 MPG divisor.

What to do. Write down the exact series name from the fuel clause, then check which series the invoice’s diesel price matches. If the contract says “the DOE index” with no qualifier, you have agreed on a family of numbers and the carrier picks from it. That is a contract finding, not an invoice finding, and the fix is at renewal. A regional index is defensible when a carrier runs a dedicated fleet inside that region, and much harder to defend on a Dallas to Memphis lane billed off the California series.

Check 2: Which DOE week applies

This is the check that finds the most money, because the error is systematic rather than random.

EIA captures the price as of 8:00 a.m. local time on Monday and publishes the following morning, per its published survey methodology. One number per week, fixed once published. There is never ambiguity about what a week’s price was, only about which week your contract selects. Three conventions are common, and all three are defensible:

• The index published on the Monday preceding the week of shipment, effective the following Monday.
• The most recently published index as of the pickup date.
• The index in effect on the delivery date.

Each one reaches later than the one above it. A carrier that defaults to a system-wide delivery-date rule while the contract specifies the preceding Monday is always grabbing a fresher week, and on a rising market a fresher week is a higher price. That is why these variances do not cancel out.

What to do. Find the effective-date clause, note the words used (“preceding,” “in effect on,” “week of shipment,” “date of pickup,” “date of delivery”), then pull the ship date off the BOL rather than the invoice header and look that week up in the EIA series. The full mechanics, including what one week of lag costs across a lane, are in which DOE week applies to your fuel surcharge.

Sort by direction, not size. A batch where nearly every variance favors the carrier is a configuration error worth fixing once at the carrier level. Variances scattering both ways by pennies are rounding. Leave those alone.

Check 3: The peg and the MPG divisor

For truckload, the formula is (index - peg) ÷ MPG × miles. Two of those four inputs are pure contract terms and both drift.

The peg. A base price near $1.25 still turns up in contract templates copied forward for years. If your linehaul was negotiated against materially higher diesel, a low peg charges you for the same fuel twice: once inside the line rate and again in the surcharge. Ask what diesel price the linehaul assumes. If nobody can answer, the peg is a number rather than a basis.

The MPG divisor. A lower assumed fuel economy produces a larger surcharge. Unlike the peg, this is a factual claim about equipment, which makes it arguable with data rather than only at renewal.

What to do. Confirm the peg and MPG on the invoice or in its basis field match the contract. That is the audit. Whether those are good numbers is a negotiation, and the full sensitivity math is in how to calculate a truckload fuel surcharge from the DOE index.

The LTL version. LTL has no peg and no MPG, just a published bracket table keyed to the same EIA number, with a version and an effective date. Confirm the invoice used the table in effect on the applicable date, not a newer republished one. Then read the bottom row: a nonzero lowest bracket is a floor above zero, a permanent addition to linehaul that no longer varies with fuel. What happens at the bottom of the range on both mechanisms is covered in what happens to your fuel surcharge below the base price.

Check 4: What the surcharge is applied to

Same charge, two different bases depending on mode, and each has its own failure.

Truckload: the mileage basis. The miles in the fuel formula should be the same miles the linehaul was rated on. Practical miles and shortest miles from the same routing engine differ on the same lane, and engine versions differ from each other. That difference flows into both the linehaul and the fuel, so a mileage discrepancy is never a single-line error. Check which engine the contract names, which version, and whether it specifies practical or shortest, then compare the invoice miles against the rate confirmation. If they differ, dispute the fuel and the linehaul together.

LTL: gross or discounted linehaul. The LTL surcharge is a percentage of linehaul, so the order of operations decides the total. A 40 percent surcharge on a $1,000 gross linehaul is $400. The same surcharge computed after a 65 percent discount is $140. That is not a rounding difference, it is the largest single variable on the invoice, and the contract has to say which applies.

What to do. Write down the base the contract specifies, then reproduce the invoice’s fuel amount from it. If you cannot reproduce it from the stated base but you can from the other one, you have found it.

Check 5: What the surcharge is applied on top of

This is the check almost nobody runs. Does the fuel surcharge touch accessorials? On many invoices the fuel percentage is applied to linehaul only. On others it is applied to linehaul plus some or all accessorial charges. A surcharge riding on a liftgate fee, a detention charge, or a lumper reimbursement is defensible if the carrier’s rules tariff says so, and an overcharge if it does not. Accessorials run from equipment charges to labor charges to pass-through costs (see the practitioner taxonomy of accessorial charges for the range), and whether fuel touches any of them is a contract question, not a regulatory one.

What to do. Divide the fuel line by the linehaul. If the result exceeds the applicable percentage, work out which other charges have to be in the base to produce it, then request the tariff item number and effective version and read what it covers.

The compound version. If an accessorial should never have been billed at all, the fuel computed on it goes too. Carriers frequently credit the charge and leave the fuel, because the credit is issued by a person and the fuel was computed by a system. Ask for both.

Check 6: The arithmetic and the rounding

Now recompute. This takes thirty seconds once you have the five inputs above.

Truckload. (index - peg) ÷ MPG = dollars per mile, then × billed miles. Carry the per-mile figure to four decimals before you multiply. Carriers publish it rounded to the cent or to a tenth of a cent, and which convention they use changes the total by a few dollars per load: not worth a phone call once, worth noticing at 400 loads a month.

LTL. Find the bracket the applicable week’s price falls in, take the percentage, apply it to the correct base. Bracket boundaries are where LTL fuel errors concentrate: inside a bracket a nine-cent diesel move changes nothing, and at a boundary a one-cent move changes the percentage on every shipment. A wrong-week error that lands on the other side of a step shows up as a clean half-point difference across that week’s invoices.

Then check for a second fuel line. Corrected bills, rebills, and consolidated invoices all create opportunities for fuel to be assessed twice, and the second one rarely looks like a duplicate because the invoice number is different.

And sanity-check the ratio. Divide the surcharge by the linehaul and compare across carriers on similar lanes. If most land near 23 percent and one bills 41 percent, one of the inputs is different, and finding out which comes before anything else on that carrier.

When the invoice will not tell you the basis

Half of these checks stall if the fuel line is a bare dollar amount. You are entitled to better. Under 49 CFR 373.103, a freight or expense bill must show the exact rates assessed and the total charges due with the nature and amount of each charge, alongside origin and destination, shipment date, package count, freight description, weight or volume, route, participating carriers, and remittance address. A line reading “FSC 412.80” with no basis is a defective bill on its face, and asking for the index, the week, and the rate applied is a reasonable request with a rule behind it.

Do not overstate it. Nothing in that regulation says the fuel program has to be fair, or that the peg has to be current, or that the surcharge cannot touch accessorials. It says the bill has to tell you what it charged. That is enough: once you have the basis, the argument is arithmetic rather than opinion.

Writing it up

Fuel disputes settle faster than any other billing dispute, because there is no judgment involved. Either the inputs match the contract or they do not. Put the recomputation in the body of the email, not in an attachment: the clause quoted verbatim, the BOL ship date and the index week it selects, the published price for that week with a link to the EIA page, the arithmetic line by line, the difference against the invoiced amount, and a specific ask with a date.

If you found a pattern across a batch rather than one bad invoice, say so in those terms. “Your system is applying the delivery-date index where our contract specifies the Monday preceding shipment” gets routed to someone who can change a configuration. “Invoice 48213 looks high” does not.

Mind the clocks. Under 49 U.S.C. 13710, a shipper must contest a bill within 180 days of receipt to preserve the right to challenge. If you already paid, this is an overcharge claim: under 49 CFR 378.4 it should come with the freight bill and the rate or tariff authority relied on, and under 49 CFR 378.8 the carrier must pay, decline, or settle it within 60 days absent a written agreement to extend. The rest of the clocks are in every freight billing deadline that can cost you money.

If you are the shipper

Run checks one, three, and four once per carrier, not once per invoice. Those are contract facts and they do not change between loads. Run checks two, five, and six on a sample every month. When you find a pattern, take it to the carrier as a billing configuration issue rather than a fight over one bill. Most will fix it without escalation, because the fix costs them nothing and the alternative is you auditing every invoice forever. The recomputations are also your negotiation file: a quarter of them tells you what the peg and MPG in your contract are worth in dollars, which beats asking for a better peg on principle.

If you are the broker

You have two fuel programs per load, one on the customer rate confirmation and one on the carrier agreement, frequently built on different pegs, different MPG divisors, or different effective-date conventions. Each gap is margin in whichever direction it points, and it stays invisible in a load-level P&L because both numbers look correct in isolation.

Reconcile the two clauses against each other before you reconcile a single invoice, using the field-by-field method in reconciling a rate confirmation against the carrier invoice. Where they differ, either align them at renewal or price the gap in deliberately. And watch check five: fuel your carrier applied to an accessorial you did not pass through is a pure margin leak.

The copy-paste version

Paste this into your AP checklist or your invoice review template.

1. Index series. Does the price used match the series the contract names? National, PADD, or California.
2. Applicable week. Does the index week match the contract’s effective-date rule, measured from the BOL ship date?
3. Peg and MPG. Do both match the contract? For LTL, does the bracket table version and effective date match?
4. Base. Truckload: do the fuel miles match the linehaul miles and the contracted mileage engine? LTL: gross or discounted linehaul, per the contract?
5. Scope. Is fuel applied to accessorials? If so, does the rules tariff say it can be?
6. Arithmetic. Recompute to four decimals, check rounding, check for a second fuel line on a rebill, and compare the fuel-to-linehaul ratio against your other carriers.

Six checks, about five minutes per invoice the first time and under a minute once you know the carrier. Run it by hand on twenty invoices before you decide whether to keep doing it by hand. That gives you your own error rate, which is the only input that settles the build-or-buy question, and the rest of that math is in what freight audit really costs across three pricing models.

Sources

• EIA, On-Highway Diesel Fuel Price Survey methodology (Form EIA-888, 590 retail outlets, cash self-serve pump price including taxes as of 8:00 a.m. local Monday, published Tuesday morning, Wednesday when Monday is a government holiday)
• EIA, Gasoline and Diesel Fuel Update (week ending July 27, 2026: U.S. average $5.313 per gallon, Gulf Coast $5.087, California $6.670)
• EIA, Weekly U.S. No 2 Diesel Retail Prices, on-highway series
• 49 CFR 373.103, Form of freight bill (Cornell LII)
• 49 U.S.C. 13710, billing and contesting windows (Cornell LII)
• 49 CFR 378.4, Documentation of overcharge claims (Cornell LII)
• 49 CFR 378.8, Disposition of overcharge claims within 60 days (Cornell LII)
• Top 20 accessorial charges, practitioner taxonomy (Zipline Logistics)
• FreightWaves, Fuel surcharges in trucking (trade-press explainer on how surcharges are set, updated, and negotiated)