What is demurrage? It’s rent. More precisely, it’s the daily fee a carrier or terminal charges when a loaded container sits at the port after its free time runs out. Detention is the cousin. Same idea, different place: the container has left the terminal (usually for a warehouse or a chassis) and hasn’t come back empty yet. Both clocks start the day free time ends. Neither stops on its own. Most demurrage charges and detention fees trace back to planning that happened, or didn’t, before the ship arrived.
Importers shipping through Houston or any other U.S. port can work with Posey International to plan around free time from the booking stage.
What does demurrage actually mean in shipping?
The word comes from an old French verb meaning “to delay.” Fitting.
Terminals exist to move boxes. Not store them. So when a vessel discharges, each container gets a short grace period, called free time, for the consignee to clear customs and pull it out. A few days is common, though the real number depends mostly on the carrier and the port. Importers with volume can sometimes negotiate more. After that? Demurrage, every day, until the full container exits the gate.
Picture a manufacturer bringing machinery parts into Houston. The ship arrives Monday. A paperwork problem holds customs release into the next week, and free time ended Thursday. Every day after Thursday lands on the bill. The parts haven’t moved an inch.
What does detention mean in shipping?
Detention picks up where demurrage leaves off. A trucker hauls the full container out of the terminal, and a new clock starts. The importer gets a set number of days to unload the box and send the empty back to wherever the carrier wants it. Go over, and the carrier bills detention.
Some U.S. carriers and truckers call this per diem. Same meaning, usually.
There’s a wrinkle, though. Some motor carriers also bill chassis per diem for the trailer the box rides on, and that’s often stacked on top of the ocean carrier’s detention.
Detention tends to bite importers whose warehouses can’t unload fast. Maybe the dock’s already full. Maybe a delivery appointment slipped. Either way, the empty sits in a yard and the meter keeps running.
Demurrage vs detention, side by side
Location is the easiest tell.
| Charge | Demurrage | Detention |
| Where the container is | Inside the port terminal | Outside the terminal (warehouse, yard, chassis) |
| Container status | Usually loaded (full) | Full while unloading, then empty until returned |
| Clock starts | When terminal free time expires | When the container leaves the terminal (after its own free days) |
| Clock stops | When the full container exits the gate | When the empty is returned to the carrier |
| Typical cause | Customs holds, late pickup, missing documents | Slow unloading, warehouse congestion, delayed empty return |
One container can rack up both on the same shipment. It sits at the terminal past free time while a customs hold gets sorted out. Then it sits at the warehouse past its detention days because the dock was booked. Two invoices. One delay, and it started upstream.
Some carriers pool the days instead, offering combined free time that covers the terminal and outside periods together. At some ports, the terminal operator also bills its own storage charges on top. The contract and the carrier’s tariff spell out which setup applies, so it’s worth reading both before the ship sails.
Why do these charges pile up?
Usually it’s one of a handful of predictable problems.
- Customs holds. An incomplete commercial invoice or a wrong tariff classification can stall release. So can a missing customs bond. Nothing leaves the terminal until CBP says so.
- Paperwork that doesn’t match. A bill of lading that disagrees with the invoice can trigger holds and inspections, and a late Importer Security Filing (ISF) can too.
- Trucking capacity runs thin in peak season, and finding a drayage carrier with an open appointment can take longer than free time allows.
- Warehouse congestion. The facility can’t unload, so the box sits on a chassis. Detention builds.
- Port congestion. Some terminals require pickup appointments, and when none are open, containers just wait.
- Visibility. The vessel showed up early and nobody noticed. Free days are gone before clearance even starts.
What do these have in common? Coordination. Freight, customs, trucking and warehousing all have to line up, and the charges show up in the gaps between them.
How importers avoid demurrage and detention
Clear customs before the ship docks
CBP accepts entry filings before cargo lands. When a licensed customs broker files the entry and the ISF early, cargo is often ready for release right around discharge. That saves the whole free-time window for pickup instead of burning it on paperwork. It’s the most direct fix there is, and it’s why the choice of customs broker matters so much on ocean shipments.
Negotiate more free days
Free time isn’t always fixed. Importers with steady volume can often get extra days written into their service contracts. Timing matters, though. That conversation goes better during annual contract talks than after a container’s already accruing charges.
Book trucks and dock slots early
Reserve drayage and warehouse receiving as soon as the ETA firms up. Last-minute scrambles are where free days quietly disappear.
Watch the vessel every day
Ships arrive early. They get delayed, or skip ports entirely. Checking the vessel and each container’s availability date daily catches changes before they turn into invoices.
Transload when the warehouse is jammed
If the receiving warehouse can’t take a container in time, unloading at a nearby facility and returning the empty right away can beat paying daily detention. That’s where short-term warehouse storage near the port earns its keep.
Keep freight and customs with one team
When the forwarder and the broker are separate companies, handoffs get dropped. One side sees the arrival notice. The other doesn’t file until somebody forwards an email. An ocean freight forwarder with brokerage in-house closes that gap. Posey International has kept freight forwarding and customs brokerage under one roof since 1974, and Licensed Customs Broker Abraham Garza (LCB) leads the customs side.
What the FMC billing rule changed
The Ocean Shipping Reform Act of 2022 told the Federal Maritime Commission to tighten how carriers bill these charges. The FMC’s final rule took effect May 28, 2024. Here’s what matters to importers.
- Who gets the bill. Only the party that contracted for the transportation (usually the shipper) or the consignee. Carriers can’t just send it to the trucker anymore.
- Invoices have a deadline. Ocean carriers get 30 calendar days from the last charge to issue one, and NVOCCs get 30 days from when they receive the carrier’s invoice.
- Disputes. The billed party has 30 calendar days from the invoice date to dispute the charges and request relief. The carrier then has 30 days to try to resolve it.
- Late means unpaid. If a carrier misses the timing rules, the billed party isn’t obligated to pay.
The rule also spells out what an invoice has to show, like the container number and the free-time dates. When it took effect, those content requirements were put on hold pending a federal paperwork approval. Check where that stands before leaning on it.
So what does this mean in practice? A demurrage invoice that shows up months late may not be enforceable. Every invoice deserves a check against the real container dates. Before anyone pays it.
Frequently Asked Questions
Who pays demurrage costs?
Depends on the deal. The party that contracted for the ocean transportation or the consignee receiving the cargo is responsible, and which one actually pays comes down to the Incoterms and the sales contract between buyer and seller. One thing’s settled now. Under the FMC rule, carriers can’t bill truckers or other third parties for these charges.
Are demurrage and storage the same?
No. Demurrage is the carrier’s charge for its container sitting in the terminal. Storage is the terminal operator’s fee for yard space. Some ports bill both for the same days.
What is free time for demurrage and detention?
It’s the grace period: a set number of days a container can stay in the terminal, or out of it, before charges start. The carrier’s tariff or the shipper’s service contract sets it. Some carriers split it into separate demurrage and detention days. Others pool them.
How much is demurrage per day?
There’s no single rate. Each carrier publishes its own tariff, and the price moves with the port and the container size (a refrigerated box usually isn’t priced like a standard dry one). Most tariffs are tiered, too, so the daily rate climbs the longer a container stays. A delay of several extra days can cost a lot more than day one suggests.
Is demurrage a penalty?
It’s not supposed to be. The FMC’s view is that these charges exist to get cargo and equipment moving, not to generate revenue. If a charge couldn’t have changed the importer’s behavior (say, the terminal was closed), it may be worth challenging.
Getting ahead of the clock
Got a container stuck at the port, or a detention invoice that doesn’t add up? Posey International’s Houston office handles ocean and air freight along with customs brokerage. For cross-border moves, the Brownsville office sits right on the US-Mexico border. Importers can request a quote or ask a question through the Posey International contact page, and the team will route it to the right office.
