What is detention in shipping?
On an import, the detention clock starts when the full container leaves the terminal and stops when the empty is returned to the depot the line names. On an export, it runs from collection of the empty until the loaded box is gated back into the terminal. Once free time is used up, the line bills per container per day, usually on a rising scale.
Detention is the outside-the-port counterpart of demurrage, and carriers often invoice the two together as “D&D”. The word has a second meaning in North American trucking: a fee a trucking company charges when its driver is kept waiting at pickup or delivery beyond the agreed free hours. Check which one an invoice means before disputing it.
Typical causes are slow unloading at the consignee's warehouse, a late return of the empty or a return to the wrong depot. Book the delivery slot before the container is collected, keep the equipment interchange receipt as proof of the return date, and for cargo that takes days to unload, consider stripping it at a warehouse near the port and returning the box at once.