Fuel Surcharge (BAF) Explained — and How to Verify It on Your Freight Invoice
The fuel surcharge is the single most common variable line on a freight invoice — and one of the easiest to get wrong, because it's a moving percentage tied to an external index. If the rate applied doesn't match the index for the shipment's period, you overpay. Here's what it is and how to check it.
What is a fuel surcharge?
A fuel surcharge is an adjustment carriers add to the base freight rate to pass through changing fuel costs. Because fuel prices move constantly, carriers don't rebuild their base rates every month — they publish a surcharge, usually as a percentage of the base freight, that tracks a fuel index.
You'll see it under several names:
- Road: "fuel surcharge", "Kraftstoffzuschlag", "Dieselfloater".
- Sea: BAF (Bunker Adjustment Factor) — and CAF (Currency Adjustment Factor) alongside it.
- Air: fuel surcharge per kg of chargeable weight.
(See the glossary for BAF, CAF, and related surcharge terms.)
How it's calculated
The mechanics vary by mode:
- Road: typically a percentage of the net freight, set monthly from a published diesel index (for example a national statistics-office road-fuel price). The carrier defines a base price and a step table: as the index rises, the surcharge percentage rises with it.
- Sea (BAF): often a fixed amount per container or per ton, revised quarterly or monthly per trade lane.
- Air: usually a rate per kilogram of chargeable weight, updated periodically.
The key point: the surcharge for a given shipment depends on the period the shipment moved in and the index value for that period. Apply last quarter's higher percentage to this quarter's shipment and the customer overpays.
Where fuel-surcharge overcharges hide
- Stale percentage — the surcharge from a previous, higher index period applied to a current shipment.
- Wrong base — the percentage applied to a larger base than the agreed net freight (e.g. applied after other surcharges, compounding).
- Surcharge on exempt charges — fuel applied to line items it shouldn't touch.
- Index mismatch — a percentage that doesn't correspond to any published index value for the period.
Because the percentage looks legitimate, these are rarely questioned.
How to verify it
To check a fuel surcharge you need the agreed index and base mechanism, the shipment's date, and the billed surcharge. Confirm: (1) the percentage matches the index value for that period, (2) it's applied to the correct base (usually net freight only), and (3) it isn't double-applied. If the billed percentage is higher than the index justifies, that's a recoverable overcharge.
Sentra holds the surcharge schedule with its validity periods and checks each shipment's fuel charge against the value that applied on the shipment date — so a stale or inflated percentage is flagged rather than paid, and confirmed cases flow into an evidence-backed dispute.
FAQ
What does BAF stand for? Bunker Adjustment Factor — the fuel surcharge used in sea freight, adjusting for changes in bunker (marine fuel) prices. CAF, the Currency Adjustment Factor, is a related surcharge for exchange-rate movements.
Is a fuel surcharge a percentage or a fixed amount? It depends on the mode. Road fuel surcharges are usually a percentage of net freight; sea BAF is often a fixed amount per container or ton; air is typically per kilogram. All track a fuel index over time.
How do I know if my fuel surcharge is too high? Match the billed percentage (or amount) to the published index value for the period the shipment moved, and confirm it's applied to the correct base. A surcharge that doesn't correspond to the index for that period is a candidate for dispute.
--- Related: Rate validation · Disputes & evidence · Glossary: BAF, CAF, fuel surcharge