Detention vs demurrage: detention is for the carrier's container kept outside the terminal past free time; demurrage is for a loaded container left inside the terminal past free time.
What are detention charges in shipping?
Detention is the charge an ocean carrier assesses, per container and per day, when a shipper, consignee or its trucker keeps the carrier's container outside the port, rail ramp or depot beyond the allowed free time. It pays for the equipment, not for terminal space, which is what demurrage covers. The FMC's rules define demurrage and detention together as any charges, including "per diem" charges, related to the use of marine terminal space or shipping containers, not including freight (46 CFR 541.3).
Detention vs demurrage vs per diem
| Detention | Demurrage | |
|---|---|---|
| Pays for | The carrier's container | Terminal space |
| Where the container is | Outside the terminal: on the road, at your dock or in a yard | Inside the terminal |
| Import clock | Gate-out to empty return | Discharge to gate-out |
| Export clock | Empty pickup to loaded gate-in | Gate-in to loading |
| Who bills | Ocean carrier | Ocean carrier or marine terminal operator |
In US drayage, per diem and detention are used interchangeably. The Port Authority of New York and New Jersey's truckers' guide defines per diem as a fee the steamship line charges a trucker for late return of equipment. The trucker normally bills it on to the importer or exporter whose container it was, so the cost lands with the cargo owner either way.
How detention charges accrue
- Per container, per day, counted from the day after the last free day for detention until the container is back where the carrier said to return it
- Tiered rates: a first daily rate for the first block of days after free time, then higher rates for later blocks, so the cost per day rises the longer the container is out
- Combined or separate free time: some tariffs and contracts give separate demurrage and detention free days, others one combined allowance from discharge, so a container that sat in the terminal may reach the road with fewer detention days left. Check the last free day for the empty return, not just the port LFD
- The chassis is separate: a chassis kept with the container is charged by the chassis provider under its own terms
Two examples
US import, slow unload. A US importer's container is dropped at its warehouse on the last free day for demurrage. The dock is full, the container waits there several days, and the empty goes back after the detention free time has ended: detention runs for every day until the empty is returned, even though the container was on time out of the port. Transloading near the port, or a live unload, ends the clock sooner.
Indian export, documents late. An exporter picks up an empty, stuffs it at the factory, then waits on an inspection certificate or a buyer's approval before the shipping bill can be filed. The export detention clock runs from empty pickup until the loaded container is gated in at the port, under the carrier's local tariff. The FMC's charge complaint procedure does not cover charges on export cargo loaded at a non-US port.
How to avoid detention
- Ask the carrier where the empty goes before you unload; a return to a distant depot takes days of the free time
- Live unload where you can, and have labor and a dock ready for a dropped container
- Transload near the port when the goods go on to several places; emptying the container early ends the clock
- On exports, pick up the empty only when the cargo and documents are ready, not days ahead
- Book drayage for the empty return as well as the delivery, and keep the equipment interchange receipts from pickup and return: they are the proof in any dispute
- Check each invoice against the part 541 list below before paying
The US rules: OSRA 2022 and the FMC
- Ocean Shipping Reform Act of 2022 (Public Law 117-146, enacted June 16, 2022): a common carrier may not invoice demurrage or detention unless the invoice shows the charges comply with the FMC's rules, and an invoice without the required information does not have to be paid (46 U.S.C. 41104). The Act also lets anyone assessed a carrier charge ask the FMC to investigate it; on demurrage or detention the carrier must show the charge was reasonable (46 U.S.C. 41310)
- Interpretive rule, 46 CFR 545.5: absent extenuating circumstances, detention imposed when it does not serve its incentivizing purpose, such as when empty containers cannot be returned, is likely to be found unreasonable (545.5(c)(2)(ii))
- Billing rule, 46 CFR part 541 (effective May 28, 2024): the invoice must be issued within 30 calendar days of the last day the charge was incurred, or 30 days from the carrier's invoice when an NVOCC passes it on, or it need not be paid (541.7). It must show the bill of lading and container numbers, why the billed party is liable, the free time with its start and end dates, the earliest return date on exports, the dates charged, the tariff or contract rule and rate, a dispute contact and web page, and certifications that the charges comply and that the billing party's performance did not cause or contribute to them (541.6). A missing item eliminates the obligation to pay (541.5)
- Who may be billed: the section limiting who may be invoiced, 541.4, was set aside by the D.C. Circuit on September 23, 2025 and removed by the FMC effective December 29, 2025; the rest of part 541 remains in effect
Who pays detention?
The carrier bills the party its tariff or contract names, and the invoice must state why that party is liable (46 CFR 541.6(a)(4)). On imports that is usually the consignee or importer, on exports the shipper; a trucker billed per diem passes it on to the customer who kept the container. On an NVOCC booking the carrier bills the NVOCC, which bills its customer within 30 days of the date of the carrier's invoice (46 CFR 541.7(b)).
Can detention charges be disputed?
Yes. You have at least 30 calendar days from the invoice date to request mitigation, refund or waiver, and the billing party must try to resolve the request within 30 days (46 CFR 541.8). The strongest evidence for a detention dispute is proof the empty could not be returned: dated screenshots of the terminal appointment system with no return slot, gate closure notices and the carrier's return instructions. If the carrier does not resolve it, the FMC accepts charge complaints under its interim procedure, and complaints can also be filed through its formal or small claims process. This page explains what the rules say; for how they apply to your invoice, use the FMC's guidance and your own advisers.
Airlift is an FMC-licensed NVOCC (OTI 016162). Our drayage service, arranged as a non-asset, FMCSA-licensed broker, plans the delivery and the empty return together, and container tracking shows the gate-out and return events.
Related terms
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