Two containers arrive on the same vessel. One sits in the terminal for nine days waiting on a customs question. The other clears immediately, goes to a warehouse and stays in the yard for two weeks because the receiver has nowhere to unload it. Both generate charges. They are not the same charge, they are not from the same party, and confusing them is why they so often go unchallenged.
The distinction, precisely
| Demurrage | Detention | |
|---|---|---|
| Where the container is | Inside the terminal | Outside the terminal |
| What is being charged for | Occupying terminal yard space | Holding the carrier's equipment |
| Typically billed by | Terminal, via the carrier | Carrier |
| Clock starts | Discharge from vessel | Gate-out from terminal |
| Clock stops | Gate-out from terminal | Empty return to the nominated depot |
A useful shorthand: demurrage is rent for space you are occupying at the port. Detention is rent for equipment you are holding away from it.
The case where both apply
A delayed clearance runs the demurrage clock while the container sits in the terminal. When it finally clears and moves out, the detention clock starts. If the delay has already consumed the receiver's slack, the container is late back to the depot as well. One root cause, two invoices, from two different parties.
How free time actually works
Free time is the allowance before either clock begins charging. It is granted separately for demurrage and detention, and the two allowances are frequently different lengths.
- Free days are usually calendar days, so weekends and holidays consume them.
- The allowance is set at booking and is a negotiable commercial term, particularly for regular volume.
- Rates commonly escalate in tiers: the tenth day past free time can cost several times the first.
- Some carriers combine the two into a single merged allowance, which changes the arithmetic entirely.
Why these charges are so common
Almost every avoidable demurrage or detention charge traces to the same sequencing error: the clearance and delivery process was planned against the vessel's arrival date instead of against the free-time allowance.
Arrival is when the clock starts. Planning from it means the process begins with zero slack. Planning from the free-time expiry means working backwards to establish when the entry has to be lodged, when drayage has to be booked and when the receiving dock has to have a slot, and discovering the conflict while there is still time to resolve it.
What actually prevents them
- 01Negotiate free time at booking, against the receiver's real unload capacity rather than an optimistic one.
- 02Lodge the customs entry before arrival where the trade permits it, so release is available at discharge.
- 03Pre-book drayage and the delivery appointment rather than arranging them once the container has landed.
- 04Use drop-and-hook where the unload is slow: it removes the driver's waiting time and shortens equipment holding.
- 05Where a delay is unavoidable, ask for an extension before free time expires. Afterwards, it is a credit request, and those rarely succeed.
None of this eliminates the risk of a customs examination or a terminal congestion event. It does mean that when one occurs, the free time has not already been spent on things that were entirely within your control.
Published 8 July 2026.
