How are fuel surcharges calculated?

Most fuel surcharges are a percentage of freight, looked up in a table keyed to a published fuel price such as US Gulf Coast jet fuel or a national diesel price, averaged weekly or monthly and applied with a lag. Others are a fixed percentage, a per-kilogram scale, or included in an all-in rate.

What is an emergency fuel surcharge?

An emergency fuel surcharge is an extra charge a carrier adds when fuel prices rise faster than its regular surcharge table can follow. It should be temporary, so check that your contract allows it and that it ends once the regular surcharge has caught up.

Why did my fuel surcharge not go down when fuel prices fell?

Either the clause follows the index with a lag or in bands, so the fall reaches the invoice later, or the surcharge was stepped up or fixed and is no longer linked to an index. Ask the carrier which index and lag apply, then recompute the last three months.

Fuel Surcharge 2026: Same Fuel Shock, Very Different Bills

When fuel jumped in March 2026, one kind of fuel surcharge followed the index to the week. The rest followed their contract wording, and some never came back down.

Finding · 6 min · Sebastian Bensland, CTO, Intellyse · Published October 8, 2026 · Last updated October 8, 2026

By Intellyse, makers of freight invoice audit software · About us

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Two ground staff in high-visibility vests stand on the apron beside a hydrant dispenser refuelling an airliner under its wing — Photo: Chiara Coetzee on Flickr, CC0

Key takeaways

When US Gulf Coast jet fuel rose by about two thirds from February to March 2026, the index-linked fuel surcharges in our audits followed it two weeks later, with a correlation of 0.997, on the way up and on the way down.
Under the same diesel shock, road fuel surcharges went four ways: some grew up to twice as fast as diesel, some stepped up once and stayed, some never moved and some fell.
Emergency fuel surcharges introduced from March 2026 sat on top of a regular fuel line on more than half of the shipments that carried one, and some were still billed in September.

Most finance teams treat the fuel surcharge as a pass-through: fuel goes up, the line goes up, fuel comes down, the line follows. For surcharges tied to a published fuel table, the 2026 invoices we audited show exactly that. For the rest, the fuel line grew faster than fuel, jumped and stayed, or carried an emergency charge on top, and that difference is margin, not fuel.

How closely does a fuel surcharge follow its fuel surcharge index?

Almost perfectly, when it is tied to a published table. On the 2026 invoices we audited from carriers and forwarders that publish a fuel table, the weekly median fuel surcharge tracked US Gulf Coast jet fuel from two weeks earlier with a correlation of 0.997.

The shock itself is public. Brent crude averaged USD 71 a barrel in February 2026 and USD 103 in March, and US Gulf Coast jet fuel went from USD 2.26 to USD 3.70 a gallon (EIA via FRED). By the end of March the billed surcharge had moved from 24% of freight to 36%: about six percentage points for every extra dollar a gallon.

The link held on the way down. Jet fuel fell to about USD 3.04 a gallon in June, and two weeks later the surcharge was back at 29%. When fuel climbed again in August, the surcharge returned to 35%.

This is how fuel surcharges are calculated under such a clause: a weekly average of a named fuel price, applied after a fixed lag and looked up in a table of percentage bands. The table adds points per price band rather than scaling freight in proportion to fuel, which is why the surcharge rose by half while jet fuel rose by two thirds. It also means this week's index tells you the fuel line on invoices two weeks from now. That line is fully checkable.

Why did road fuel surcharges move so differently?

Because on road, the clause decides the invoice line, not diesel. Under the same diesel rise, US Gulf Coast diesel from USD 2.30 a gallon in February 2026 to USD 3.83 in March (EIA via FRED), the road invoices we audited showed four patterns.

Pattern	What the fuel line did	Clause it points to
Ran ahead of diesel	Fuel as a share of freight rose up to twice as fast as diesel	A steep diesel scale, or a base price set when diesel was low
Stepped up once and stayed	Jumped in a single month and did not come down when diesel dipped in June	A scale reviewed monthly or quarterly, or a renegotiated percentage
Never moved	The same percentage every month of the year	A fixed fuel percentage, not linked to any index
Fell	Fuel share went down while diesel nearly doubled	A cap on the surcharge, or a freight rate rising faster than the fuel line

On average the picture looks orderly. Across road and forwarder air freight, fuel as a share of freight roughly doubled after March, about a month behind the index. The average hides a spread wide enough that two shippers on the same lanes could see opposite movements on their fuel line.

Air freight adds one more case. On about half of the forwarder air shipments we audited, there was no separate fuel line at all, because fuel sat inside an all-in rate. A fuel charge you cannot see is a fuel charge you cannot recompute.

Why does an emergency fuel surcharge outlive the fuel shock?

An emergency fuel surcharge is an extra charge a carrier adds when fuel rises faster than its regular surcharge can follow. From March 2026 they appeared under several names (emergency fuel, emergency bunker, emergency fuel import and export), and on more than half of the shipments that carried one, the invoice also carried the regular fuel surcharge.

Its only job is to bridge the lag. The charts above show how long that lag is: two weeks for a weekly table, about a month for road. After that, the emergency line charges for fuel the regular line already covers.

Some carriers removed theirs after a single month. Others were still billing them in September, six months after the jump. On some air shipments, an emergency bunker surcharge, bunker being the term for ship fuel, was larger than the regular fuel line beside it. The related war risk lines are covered in what carriers can bill for war risk.

Why does nobody catch the gap?

Because everyone accepts the fuel line as a pass-through, so the check stops at whether it exists and looks plausible. A surcharge of 30% or 36% looks normal next to last month's and passes approval. Nobody asks whether it moved the way fuel moved.

Any gap between how your fuel surcharge moves and how fuel moves is margin, not fuel.

The 2026 invoices show four ways that gap opens:

A steeper scale. A diesel scale with a low base price or large steps turns a two-thirds rise in diesel into a fuel line that grows up to twice as fast.
Up fast, down slowly. The surcharge is raised in the month fuel jumps and lowered months later, or never, when fuel falls.
Emergency charges left running. A temporary surcharge is still billed after the regular surcharge has caught up, so the same fuel is charged twice.
A fixed percentage lifted in the shock. A rate raised in March with no link to an index has no reason to come back down.

None of these shows up when you check that a fuel line exists. Each one shows up when you put the fuel line next to the index it claims to follow.

What should you check on your fuel surcharges?

Four checks, each doable with the contract, the invoices and a public price series:

Checking the fuel line

Tick a step to reveal the next

Classify each contract's fuel clause: index table, diesel scale, fixed percentage or all-in. For index-linked clauses, write down the reference index, the averaging period and the lag.
Recompute the index-linked lines. Take the published index for the lag in your contract, look up the band and compare it with the billed percentage. A difference of one band or more is a query.
Put an end date on every emergency surcharge. Ask the carrier in writing which index level or date ends it, and check that it stops once the regular surcharge has caught up.
Compare fuel growth, not fuel levels. Set each carrier's fuel share in a month before March 2026 to 100 and track it against the index. A line that rose faster than fuel, or did not come down when fuel did, is where to start.

Step 1 of 4

Intellyse recomputes every fuel and emergency fuel line against the contract clause and the public index, so our Invoice Approval module can stop a wrong fuel line before it is approved.

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