Detention is a per-day fee charged by an ocean carrier when one of its containers is held outside the terminal — typically at the importer's warehouse or yard — beyond the free time allowed for unloading and return. It is sometimes called "per diem" in industry shorthand.
The detention clock starts when the container leaves the terminal under the importer's chassis or under a trucker dispatched on its behalf. It stops when the empty container is returned to a carrier-designated empty-return location (often a different terminal or off-dock depot).
Typical structure:
- 4–5 calendar days of free time
- Day 6+: ~$100–$200/day, often escalating
Detention applies regardless of whose fault the delay is. Common causes:
- Warehouse backlog at the consignee facility
- Driver shortage or chassis shortage preventing return
- Empty-return restrictions (terminal full, "no empties accepted")
Detention and demurrage are different. Demurrage is for the box sitting inside the terminal; detention is for the box sitting outside the terminal once it's been picked up. The fees go to different parties — demurrage to the terminal, detention to the carrier — and are billed on different invoices.
Under the Ocean Shipping Reform Act of 2022, the FMC has aggressively pursued carrier detention practices that bill for periods when return was physically impossible (no available appointment, no open gate).