Demurrage and detention in one paragraph
Both charges compensate the ocean carrier, and sometimes the terminal, for equipment that stays in use longer than agreed. Demurrage applies while a loaded import container sits inside the terminal after free time. Detention applies while the container is outside the terminal, at your warehouse or a yard, beyond its free time, until the empty is returned. Terminology varies by carrier and by country, but in US import practice that is the usual split.
Demurrage vs detention vs per diem vs storage
The same box can trigger several charges, billed by different parties. Knowing which is which is the first step to disputing a wrong invoice.
| Charge | Where the container is | Who usually bills | Clock stops when |
|---|---|---|---|
| Demurrage | Full, inside the terminal | Ocean carrier | The container gates out full |
| Detention | Outside the terminal, full or empty | Ocean carrier | The empty is returned to the terminal or depot |
| Per diem | Outside the terminal | Carrier to the trucker, often passed to you | The empty is returned |
| Terminal storage | Inside the terminal | Marine terminal operator | The container gates out |
| Chassis per diem | On a chassis outside the terminal | Chassis provider | The chassis is returned |
In the US, "per diem" is the term many truckers use for what carriers call detention, because the equipment interchange agreement bills the motor carrier for each day it holds the box. Some carriers combine demurrage and detention into one free time allowance, so read your contract or the carrier's tariff to see which model applies.
Free time and the last free day
Free time is the number of days you may hold the container without charge. It is set by the carrier's tariff or your service contract and differs by port, by equipment type and sometimes by commodity. Free time may be counted in calendar days or in working days, and the start point differs as well, for example from discharge or from the day the container becomes available.
The last free day (LFD) is the final day you can pick up the container from the terminal without demurrage. After the LFD, charges usually step up in tiers, so the daily rate rises the longer the box stays. The LFD is the single most important date in import trucking, and it can move: if the terminal or customs places a hold, or the box is not accessible, some tariffs extend free time, others do not.
Why containers end up paying fees
Most demurrage and detention bills are not caused by one big failure. They come from small delays that nobody saw in time.
- The vessel arrives early or late and the trucking appointment is no longer valid.
- The container is discharged but nobody notices, so pickup is not booked.
- A customs, freight or USDA hold stops release and is cleared too late.
- Terminal appointments are scarce and the next free slot is after the LFD.
- The warehouse cannot unload, so the full container sits on a chassis in the yard.
- The empty is returned to the wrong depot or the return is refused.
- The paperwork for the release, such as the freight release or the delivery order, is missing.
Each of these is a timing problem. The information exists, but it is spread across the carrier site, the terminal site, the customs broker's email and the trucker's dispatch board.
How container visibility cuts demurrage
Demurrage is about the time between discharge and gate out. Visibility attacks it by moving that information to the right person sooner.
- Arrival and discharge alerts tell dispatch to book the terminal appointment as soon as the box is on the ground.
- Hold status (customs, freight, line) shows what still blocks release, while there is time to clear it.
- The last free day appears on every container, with reminders a set number of days before it.
- A filter for containers discharged but not gated out, sorted by LFD, becomes the daily pickup list.
- Transshipment and rolled cargo events warn you that the arrival date has moved before the trucker is booked.
How container visibility cuts detention
Detention runs from gate out to empty return. The useful signals here are different.
- Gate out full starts the detention clock, so record the date for every container.
- Delivery to the warehouse and the unload time show how long the box sits full.
- An empty available or empty return event confirms when the clock stopped.
- A list of containers out for more than a set number of days flags boxes forgotten in a yard.
Many detention disputes come down to the empty return date. If your records show the empty was returned on a given day and the carrier bills two more days, a timestamped return event is the evidence you need.
Dispute rules for US shippers
In the US, the Ocean Shipping Reform Act of 2022 and the Federal Maritime Commission billing rule that followed set requirements for demurrage and detention invoices. Carriers must bill the right party, include specific information such as the container number, the free time, the applicable rate and the dates the charges started and stopped, and issue the invoice within a set period after charges stop accruing. Billed parties have a window to request mitigation, refund or waiver. Missing required information is a ground to challenge the bill. Check the current FMC rules for exact time limits before you file.
A dispute is far easier with your own record of events: discharge, availability, holds and their release times, appointment availability, gate out and empty return. Without it, you are arguing against the carrier's data with no data of your own.
Who should own the last free day
Fees grow when everyone assumes someone else is watching. The importer's logistics team, the customs broker, the forwarder and the drayage company each see part of the picture, and none of them sees all of it. Assign one owner for each container's release and pickup, usually the importer's logistics coordinator or the forwarder under a clear agreement, and give that person the full timeline: vessel arrival, discharge, holds, availability, appointment, gate out and empty return. Shared visibility does not replace that owner, but it means the owner is no longer chasing information across five systems and can spend the time on the containers that are actually at risk.
A daily routine that keeps fees down
- Each morning, review containers discharged and not gated out, sorted by last free day.
- Clear any holds on containers within two days of the LFD.
- Confirm terminal appointments for every box with an LFD in the next three days.
- Review containers gated out more than five days ago with no empty return.
- Escalate any container where the vessel ETA moved by more than a day.
- Once a week, compare demurrage and detention invoices with your recorded events.
How ShipmentVisibility helps
Container tracking in ShipmentVisibility keeps every container on one list with normalized milestones for all major ocean lines: loaded, departed, transshipment, arrived, discharged, released, available, gate out and empty return. On the Pro plan and above, ocean milestones include last free day reminders, so the team gets an alert by email, Slack or webhook before the LFD, not after. Every event is stored with its time, so you have the record you need when an invoice looks wrong. Read how to track a container by number to check your numbers first, then compare plans on pricing.
Quick reference
- Demurrage: full container inside the terminal after free time.
- Detention: container outside the terminal until the empty is returned.
- Per diem: the trucker's term for daily equipment charges outside the terminal.
- Storage: the terminal's own charge for time on its yard.
- Last free day: the date to beat, and the one date every container should show.