These three charges are routinely confused, and the distinction matters because they are billed by different parties and avoided in different ways. Demurrage is charged by the carrier when a laden container stays inside the terminal beyond the agreed free time. Detention is charged by the carrier when the container is outside the terminal — in your yard or at your warehouse — beyond its free time, and is often billed per container per day under the name per diem. Port storage is charged by the terminal or port authority for occupying its ground, and runs in parallel with demurrage rather than instead of it. It is entirely possible to incur all three on one container.
Free time is set by the carrier, not by custom, and it varies by trade lane, port, container type and the rate you booked. Specialised equipment such as reefers, flat racks and open tops usually carries shorter free time than standard dry boxes, and the daily rate escalates in tiers, so the second week costs more per day than the first. The practical consequence is that the number you need is not a general industry figure but the specific free time written into your own booking. Ask for it at the point of booking and note the exact date the clock starts, which is normally container discharge rather than vessel arrival.
Most demurrage is caused by documents, not by transport. A bill of lading that has not been surrendered, an import declaration held for an HS code query, a missing certificate of origin needed for a preferential duty claim, a licence or permit that was never applied for — each of these stops clearance while the daily charge continues. The defence is to work backwards from the estimated arrival date and have the complete document set with your broker before the vessel berths, not after. Where a commodity is subject to inspection, quarantine or DG handling rules, allow for that examination in the plan rather than treating it as an exception.
Detention is usually caused by capacity on your own side. A container delivered on a day when the warehouse has no unloading labour, a site with no forklift for a floor-loaded container, a single dock shared with outbound orders, or an empty that sits behind the building for a week because nobody booked the return — all of these are within your control. Fix the return leg at the same time you fix the delivery leg, confirm the empty return depot before the container leaves the port, and keep the interchange receipt, because disputes over detention are settled on the date the empty was actually handed back.
Three measures reduce exposure before anything goes wrong. Negotiate extended free time at booking if your clearance or unloading pattern genuinely needs it; it is far cheaper agreed in advance than argued afterwards. Build in a buffer around public holidays at the destination, when terminals run reduced gate hours and brokers close. And nominate one person who tracks arrival dates against document readiness for every container in transit, so a problem surfaces while it is still a phone call rather than an invoice.
We monitor free time and clearance readiness on the shipments we handle, and we will tell you the free time attached to your booking before you confirm it. If you are already accruing charges on a container, send us the bill of lading and the clearance status and we will set out what can still be done.
