When you book a container move, you get a rate. Then, sometimes, the final invoice comes in higher than the quote. The difference is usually accessorial charges: the extra fees that attach to a container when something takes longer or needs more than the base move.
Accessorials are normal, and they are almost always legitimate. The trouble is that they are confusing. Different parties charge them, each one runs on its own clock, and most of them are triggered by events that happen at the port, the rail ramp, or the dock, away from the person who booked the shipment.
This guide explains the most common drayage and intermodal accessorials, who charges them, why they appear, and what a shipper can do to keep them under control. The goal is simple: fewer surprises on the invoice.
Why the final invoice can differ from the quote
A drayage quote covers the planned move: pull the container from the terminal, deliver it, and return the empty. Accessorial charges cover the exceptions, which are the moments when the container or the truck has to wait, when extra equipment is needed, or when a step takes longer than the free time allowed.
Most of those exceptions are outside the carrier’s control. A terminal appointment opens late. A container is not discharged from the vessel on time. A warehouse takes four hours to unload a box. A chassis is not available when the driver arrives. Each of those events can create a charge, and the charge often lands on a statement days after the move is finished. That is why the invoice can be correct and still look different from the original rate.
The three charges people mix up: demurrage, per diem, and detention
These three cause more confusion than anything else in container shipping, partly because the words get used loosely. They are not the same charge, and they are not billed by the same party. Here is the clean version.
Demurrage
Demurrage is charged by the terminal or port when a loaded container sits inside the terminal beyond its free time. In other words, the box was available to pick up, but it stayed at the port too long. Demurrage is meant to push containers out of the terminal and keep the yard moving. The clock runs at the terminal, and the charge usually traces back to whoever was responsible for arranging the pickup.
Per diem
Per diem is charged by the steamship line for the use of the container itself beyond the allowed days. It is a daily charge on the equipment, and it can keep running after the container has left the terminal, while the box is at a warehouse being unloaded or waiting to be returned empty. Per diem is about the container as an asset, not about the space at the port.
Detention
Detention, in the drayage sense, is charged when the truck and driver are held at the shipper or consignee beyond the free time allowed for loading or unloading. If a driver arrives for a live unload and waits five hours, that waiting time becomes a detention charge. Detention is about the truck and the driver’s time, not the container or the terminal.
One way to keep them straight: demurrage is the terminal’s clock, per diem is the steamship line’s clock on the box, and detention is the truck’s clock at your door. A single delayed container can trigger all three.
Free time is the clock behind most of these charges
Almost every charge above comes back to free time. Free time is the number of days or hours you are allowed before a charge starts: free time at the terminal before demurrage, free days on the container before per diem, and free time at the dock before detention.
Free time runs out for ordinary reasons. Port congestion delays the pickup. Rail ramp appointments are tight. A warehouse cannot take the container for two days. A chassis is not available, so the box cannot move. A customs exam holds the container. None of these require anyone to make a mistake. They just need the clock to run longer than the free time allowed.
Because free time is the trigger, the single most useful thing a shipper can do is know exactly how much free time each move includes and treat it as a deadline, not a guideline.
Other accessorials you may see on a container move
Beyond the big three, several other charges show up regularly in drayage and intermodal. None of them are unusual. They reflect real work or real equipment.
Chassis charges cover the use of the chassis that carries the container. A chassis split happens when the chassis and the container are in different locations, so the driver has to make an extra trip to bring them together. A pre-pull is when the container is pulled from the terminal early and held at a yard to avoid demurrage, which trades a terminal charge for a yard storage charge. Yard storage covers holding the container at the carrier’s yard.
Congestion surcharges apply when a terminal is severely backed up. An exam or inspection fee covers the cost when customs flags a container for a physical or X-ray exam. Reefer plug-in and genset charges apply to refrigerated containers that need power in transit or at a yard. Overweight or scale charges apply when a loaded container is heavy enough to need special permits or routing. A dry run or truck ordered not used (TONU) charge applies when a driver is sent for a container that is not ready. After-hours charges apply when a delivery has to happen outside normal windows.
Why accessorials get missed, delayed, or disputed
Here is the part that frustrates everyone. The events that create accessorials happen in operations, but the charges show up later in billing. A driver knows he waited four hours. A terminal storage fee appears on a port statement three days after the move. A chassis split is obvious to dispatch but invisible to the person reviewing the invoice.
That gap between the event and the invoice is where disputes begin. A shipper sees a charge with no context and questions it. A carrier knows the charge is valid but does not have the backup attached. By the time the documents are gathered, the invoice is already late. Clear documentation at the moment the event happens is what prevents most of these disputes.
How shippers can keep accessorial charges under control
You cannot remove accessorials, because they reflect real costs. You can reduce them and avoid surprises with a few habits.
Know your free time on every move, for the terminal, the container, and the delivery, and treat the soonest expiry as your deadline. Book delivery and return appointments as early as possible, because the calendar fills up and late appointments burn free time. Unload live containers quickly and return empties promptly, since per diem keeps running until the box is back. Give your carrier accurate references and paperwork up front, so nothing stalls at the gate. Ask for backup on any accessorial you do not recognize, because a good carrier can show the gate ticket, the timestamp, or the terminal statement behind it.
Most of all, work with a carrier that communicates before the charge happens, not after. A quick heads-up that a container is approaching last free day is worth more than a tidy invoice after the fact.
The back-office side: why accurate billing protects everyone
There is a reason some carriers and brokers handle accessorials cleanly and others do not, and it has little to do with the rates. It is the back office. The companies that bill accessorials accurately have a disciplined process for capturing each event, attaching the backup, auditing the carrier invoice, and getting the customer invoice right the first time.
That work has a name. A pre-billing revenue audit is the review that checks a shipment file for detention, per diem, demurrage, chassis, and other billable events before the invoice goes out, and confirms the documentation behind each one. It is also where carriers catch charges they would otherwise absorb as a cost. A great deal of margin slips away before the invoice is ever sent, simply because an event in operations never reached billing.
For drayage carriers, brokers, and 3PLs that move containers and want this handled consistently, ClearLane runs that back-office process: document and POD chase, carrier invoice audit, accessorial capture, shipper billing, and accounts receivable follow-up. For a shipper, the practical takeaway is simpler. The cleaner the back office behind your moves, the fewer surprise charges and billing disputes you deal with.
Frequently asked questions
What is the difference between demurrage and detention?
Demurrage is charged by the terminal when a loaded container stays inside the port or rail ramp beyond its free time. Detention, in the drayage sense, is charged when the truck and driver are held at a shipper or consignee beyond the free time allowed for loading or unloading. Demurrage is about the container at the terminal. Detention is about the truck and driver’s time at your door.
What is per diem in container shipping?
Per diem is a daily charge from the steamship line for the use of the container beyond the allowed free days. It can keep running after the container leaves the terminal, while the box is being unloaded or waiting to be returned empty. It is a charge on the equipment, separate from demurrage at the terminal.
What is free time?
Free time is the number of days or hours you are allowed before a charge starts. There is free time at the terminal before demurrage, free days on the container before per diem, and free time at the dock before detention. When free time runs out, the related charge begins.
Why is my container invoice higher than the quote?
The quote covers the planned move. The final invoice may add accessorial charges for events that happened along the way, such as detention, per diem, demurrage, a chassis split, or a customs exam. These charges are usually legitimate, but they are triggered by exceptions that were not part of the original rate.
What is a chassis split charge?
A chassis split charge applies when the chassis and the container are in different locations, so the driver has to make an extra trip to bring them together before the move. It reflects the additional time and mileage involved.
How can I avoid demurrage and per diem charges?
Know the free time on each move and treat it as a deadline. Book delivery and return appointments early, unload live containers quickly, return empties promptly, and give your carrier accurate paperwork up front. Working with a carrier that warns you before last free day also helps.
Who pays demurrage and per diem, the shipper or the carrier?
It depends on what caused the delay and on the terms of the move. The charge often originates with the terminal or steamship line, passes through the carrier or broker, and lands with whoever was responsible for the delay. Clear documentation of why a container ran past free time is what decides where the charge belongs.
About ClearLane
ClearLane is a freight back-office operation serving freight brokers, 3PLs, trucking companies, and intermodal operators across Canada and the United States. Services include POD chase, carrier invoice audit, shipper billing, AR management, pre-billing revenue recovery, carrier compliance, and bookkeeping support.
