By Cargo Taxi Deliveries · Published October 12, 2026
Demurrage is charged by the terminal for a loaded container left inside the terminal past its free time. Per diem is charged by the shipping line for equipment kept outside the terminal too long. They are different clocks run by different parties, and avoiding both means scheduling against the last free day rather than the arrival date.
Two clocks, often confused
Demurrage and per diem get used interchangeably and are not the same thing. Demurrage is charged by the marine terminal for a loaded import container that remains inside the terminal beyond its allotted free time. The terminal wants its yard back; every container sitting in it is space not available for the next ship.
Per diem — also called detention, confusingly — is charged by the shipping line for its equipment being kept outside the terminal longer than permitted. Once a container leaves the gate, the line is waiting for its box back, and the clock on that is separate from the terminal's.
The practical consequence is that a container can clear demurrage perfectly and then accumulate hundreds of dollars of per diem sitting empty at a consignee's yard because nobody arranged the return. Both clocks have to be managed, and they are managed by different conversations.
| Row label | Demurrage | Per diem / detention |
|---|---|---|
| Charged by | Marine terminal | Shipping line |
| For | Loaded container inside the terminal | Line equipment held outside the terminal |
| Clock starts | Discharge / availability | Gate out |
| Clock stops | Container collected | Empty returned |
| Typical free time | A few days | A few days |
| Usually caused by | No appointment, late customs clearance | Slow unload, no empty return booked |
Free time does not start when you think
The most common and most expensive misunderstanding is about when the clock starts. It is not the date the vessel berthed, and it is not the date you were notified. Free time runs from discharge or from availability depending on the terminal's tariff, and those dates can be several days apart from anything on your own paperwork.
Customs clearance is a separate matter again. A container that is available from the terminal's point of view but held for customs examination is still accruing demurrage in most tariffs, which strikes people as unfair and is nonetheless how it works. The only defence is to clear early rather than at the last moment.
The instruction that saves the most money is also the simplest: find out the last free day, in writing, as soon as the container is notified, and give that date to whoever is collecting it. Everything else follows from that one number.
The appointment is the real constraint
At the Ports of Los Angeles and Long Beach, terminal appointment systems govern. Slots are finite, they are released on the terminal's schedule, and in busy periods they go quickly. A trucker with every credential in existence and no appointment is exactly as stuck as one with none.
This is why urgency is a poor substitute for notice. A customer calling on the last free day wanting a container moved today is asking for an appointment that may simply not exist, and no amount of willingness changes that. A customer calling three days earlier gets a slot. The single highest-leverage thing a shipper can do about demurrage is to tell the carrier early.
Why transloading often beats pulling
There is a structural answer to the per-diem clock that many shippers never consider: do not take the container at all. Transloading means the container is devanned at a warehouse and the goods move onward on pallets. The box goes back promptly because nothing downstream depends on it, and the per-diem exposure largely disappears.
The second advantage is distribution. A container whose contents are destined for several consignees can be split at transload and delivered on a multi-stop route the same day, rather than being delivered whole to one party who then has to receive, sort and re-ship everybody else's freight. For a mixed container that is almost always both faster and cheaper.
The case for pulling the container intact is when a single consignee takes the whole thing, has the equipment to unload it, and can turn it around quickly. Outside that, transload deserves a serious look.