Detention
Detention is a penalty fee charged by a shipping line when the merchant holds the line's container beyond the agreed free time after it leaves the port — typically while it's at the consignee's warehouse for unpacking, or being repositioned for an export load.
Free time for detention is usually 3-5 days (sometimes longer for specialised containers like reefers). After that, charges accrue per day in tiered bands. Detention is owed by the importer/consignee or whoever holds the container.
Detention is sometimes combined with demurrage charges (which apply while the container is inside the port). The two together are often referred to as "D&D" — demurrage and detention. They are among the highest-margin revenue streams for shipping lines and one of the most controversial charges in the freight industry.
Detention is the second half of the "D&D" cost pair, and it is easy to rack up unnoticed — every day a container sits at your warehouse for unpacking, or waits to be repositioned for an export load, the meter runs. Because the free period is short (often 3–5 days), even a modest delay in unloading and returning the empty can generate a real charge.
(free days)
→ detention
An importer collects a container from the port on 1 April with 4 free days of detention. The empty is returned to the depot on 8 April — 7 days held, minus 4 free = 3 charged days. At US$90/day:
Detention = 3 × $90 = US$270, on top of any demurrage that accrued while the box was still inside the terminal.
Is detention the same as demurrage?
No. Detention is charged after the container leaves the port and is not returned empty in time; demurrage is charged while it is still inside the terminal. Both together are "D&D".
What is "per diem" in shipping?
"Per diem" is another name for detention — a per-day charge for holding the carrier's equipment beyond the free period.