What is detention in shipping?

A shipping line lends its container along with the transport. On an import, the loan outside the port begins when a truck takes the full box out through the terminal gate and ends when the empty box is handed in at the depot the line names. A number of free days is allowed for that round trip — haul, unload, return. Each day beyond them is charged as detention.

On an export the same clock runs the other way: from the day the empty container is collected from the depot to the day it is delivered full to the terminal. In both directions the line sets the free days and the daily rate in its tariff, and they vary by port, container type and contract. Time spent inside the terminal is not detention; that is demurrage, counted on a separate clock.

Detention arrives as an invoice from the shipping line, sometimes weeks after the shipment is finished, calculated from two events: the gate-out and the empty return. Both are published in the line’s tracker — our container tracking page checks a container number and points you to it — and both are also recorded on paper, because the driver is given an equipment interchange receipt at each gate.

Keep the receipt for the empty return. It shows the date, the depot and the condition of the box, and it is the document that settles an argument about when the clock stopped. Some lines bill detention together with demurrage as a single “D&D” charge against one combined allowance, and in the United States detention on the box is commonly called per diem; the invoice should still show which dates it counts.

The usual mistake is to stop watching once the cargo is out. Unloading does not end detention; returning the box does. An empty container left in a yard over a long weekend, a haulier who collects it three days later, a depot that is full and turns the truck away, a return to the wrong depot — each adds days, and the importer who was nowhere near the truck is the one invoiced.

The second mistake is planning around the wrong allowance. The free days for detention are not the free days in the port, and saving some of the first does not add to the second unless the contract merges them. Before the box leaves the terminal, know the last free day for its return and the depot’s opening hours, tell the haulier both, and if the warehouse cannot unload in time, ask the line for an extension while the days are still free.