Demurrage is the charge for a container sitting inside the terminal beyond its free time. Detention is the charge for a container sitting outside the terminal, in your or your trucker’s hands, beyond its free time.
They are billed separately, they start at different moments, and they are the two line items most likely to turn a shipment that looked profitable into one that was not.
Why the Charges Exist
A container is a physical asset that an ocean carrier owns or leases. It can only earn money by moving. Every day that box sits still is a day the carrier pays for it and earns nothing.
Free time exists because nobody can clear and return a container in a day. Ten days is not a gift; it is a workable assumption. Exceed it and the carrier recovers the cost of the asset.
The important thing for an importer is not the philosophy. It is which clock starts when.
The Two Clocks
| Demurrage | Detention | |
|---|---|---|
| Container location | Inside the terminal | Outside the terminal |
| Clock starts | On discharge, or on availability for pickup | When the container leaves the terminal |
| Clock stops | When the container leaves | When the empty is returned |
| Who bills | Terminal or carrier | Carrier |
| Typical trigger | Import clearance delay, customs exam | Slow unloading, missed return appointment |
One container can incur both, one after the other. A box stuck in the terminal for eight days and then returned late gets two bills.
What Actually Drives the Charge
It is rarely the trucking. It is one of these:
The entry is not ready. No bond, missing ISF correction, an open classification question. The container cannot be released, so it stays inside and the demurrage clock runs.
Customs orders an exam. A container pulled for inspection sits inside the terminal until CBP releases it. This is the most expensive kind of delay, because it is not a paperwork problem you can fix with an email.
Free time was calculated on the vessel arrival, not the availability date. A container that arrives on a Friday and only becomes available for pickup on Monday has already spent three days of its free time. Confirm which date the free time runs from.
The carrier appointment system is full. In congested periods the trucker may not be able to get a return appointment for several days. The container is off-hire on paper but still accruing in practice.
Free time was never confirmed in writing. This is the quiet one. Free time varies by carrier, by equipment and by the rate you negotiated. If it is not on the booking confirmation, you are working from an assumption.
Brazil, and Other Markets That Bill Differently
The demurrage and detention framework above is the US model. Other markets assign the cost differently, and this trips up importers who ship to both.
In Brazil, terminal charges are often assessed from the moment a container is discharged, and the free period is frequently shorter than a US importer expects. On top of that, storage at some terminals bills in daily tiers that escalate. An importer who budgets for the US pattern and ships to Santos can be surprised by how quickly the number moves.
The rule is the same everywhere: confirm the free time and the clock start date before the vessel sails, in writing, from the party who will bill you.
How to Avoid It
None of this is exotic. It is sequence.
- Have the entry ready before the vessel arrives. Bond in place, ISF filed and corrected, classification settled.
- Get free time in writing, with the start date named.
- Book the delivery appointment early, not when the container becomes available.
- Pre-clear anything that trips exams. Products with a history of inspection should have documentation ready before discharge.
- Track the clock, not the vessel. Once the box is discharged, demurrage is a countdown, not a status.
The counterintuitive part: the cheapest way to avoid demurrage is not faster trucking. It is a cleaner customs file.
Related Entries
Key Facts
- Demurrage = inside the terminal. Detention = outside the terminal.
- They start at different moments and are billed separately.
- One container can incur both.
- The biggest driver is a slow or incomplete customs entry, not trucking.
- Get free time in writing, with the clock start date named.
- Brazil terminals often bill from discharge, with shorter free periods than the US.