Demurrage and detention: two charges, one clock
An invoice lands for demurrage, or for detention, or for both, and the first question on the desk is which charge this actually is and whether it is right. The two charges share one starting point and split on where the container sits.
Both begin when a shipment's free time runs out. Demurrage covers a container that stays at the marine terminal past its free time; detention covers the carrier's equipment kept in use after it leaves the terminal, and in United States practice detention is billed as "per diem". Per diem is the US billing term for detention, not a third charge. The Federal Maritime Commission (FMC) defines both together, in a single phrase, as "any charges, including 'per diem' charges, ... related to the use of marine terminal space (e.g., land) or shipping containers, but not including freight charges" (46 CFR 541.3, as of July 2026). Marine terminal space is the demurrage side; use of the container is the detention side; freight is neither.
The allowance and the rate are carrier-tariff figures. Free-time allowances are not standardized: they differ by carrier, port, direction, equipment type, and contract, and are published in carrier tariff tables. For that reason this page quotes no free-time day count and no dollar rate; the current numbers live in the carrier's own tariff. How the free-time clock itself runs, from the last free day to accrual, is covered on the free-time glossary entry and the container rollovers and blank sailings guide, and is not restated here.
Demurrage vs detention at a glance
Read across each row for the distinction that decides which charge an invoice is: which resource the charge is paying for, marine terminal space or the carrier's equipment. The definitions are linked in the paragraph above; the cells here stay plain, and carry no free-time day count, rate, or carrier name.
| Charge | What it bills for | Where the container is | What resource is tied up | US billing term |
|---|---|---|---|---|
| Demurrage | A container held at the marine terminal past its free time | At the marine terminal | Marine terminal space (land) | Demurrage |
| Detention | Extended use of the carrier's equipment after the container leaves the terminal | Away from the terminal, in the importer's or trucker's hands | The carrier's container and equipment | Per diem |
How a charge builds: from free time to an invoice
A demurrage or detention charge builds in three steps, and the invoice is the last of them.
First, the carriage includes a free-time allowance, the days the container may sit at the terminal (demurrage) or stay out in use (detention) at no charge. Second, when that allowance ends, at the operational "last free day", the charge begins to accrue at the carrier's tariff daily rate for each further day the container is held. Third, the carrier, the marine terminal operator (MTO), or a non-vessel-operating common carrier (NVOCC) issues an invoice for the accrued charge.
How the free-time clock is counted, and when the last free day falls, is the free-time glossary entry and the container rollovers surface, not this page. What this page picks up is the invoice itself: it is the object the US billing rules govern, and it is where a billed party's dispute levers attach.
The US billing rules: what a demurrage or detention invoice must contain
The dispute levers below are US rules. The FMC's billing-requirements rule, 46 CFR Part 541, has been in force since 28 May 2024. It "establishes the minimum information that must be included on or with demurrage and detention invoices" and the "procedures that must be adhered to when invoicing for demurrage or detention" (46 CFR 541.1). It binds any invoice issued by an ocean common carrier, an MTO, or an NVOCC for the collection of these charges (46 CFR 541.2).
At the center of the rule is 46 CFR 541.6, which lists what a demurrage or detention invoice must contain. The invoice "must be accurate" and must carry, at a minimum, four groups of information plus two certifications:
- Identifying information: the bill of lading and container numbers, the port of discharge for imports, and the basis for why the billed party is the proper party liable for the charge. - Timing information: the invoice date and due date, the allowed free time in days, the start and end dates of free time, the container availability date (imports) or earliest return date (exports), and the specific dates for which the charge was assessed. - Rate information: the total amount due, the tariff rule or service-contract provision the daily rate is based on, and the specific rate applied. - Dispute information: contact information for a mitigation, refund, or waiver request; a digital means (such as a URL or QR code) pointing to a public description of what documentation a request needs; and defined timeframes within which the billed party must request relief and the billing party will resolve it. - Certifications: that the charges are consistent with the FMC's demurrage and detention rules, including 46 CFR 545.5, and that the billing party's own performance did not cause or contribute to the charge.
One element is worth reading carefully, because it is easy to misread as a benchmark. The timing group requires "the allowed free time in days". That is a disclosure requirement: the carrier must state its own free time on the invoice. It sets no standard or typical allowance, and there is no default number; the figure is whatever that carrier's tariff sets for that shipment.
How to dispute a charge: the levers the rules give a billed party
When an invoice looks wrong, the US rules give a billed party three concrete levers, and they sit at different strengths.
The first is a required-information check, and it is mechanical. Under 46 CFR 541.5, "Failure to include any of the required minimum information ... eliminates any obligation of the billed party to pay the applicable charge." Run the invoice against the 46 CFR 541.6 checklist above; a missing required element removes the obligation to pay.
The second is a timing check, also mechanical. Under 46 CFR 541.7, a billing party must issue the invoice within 30 calendar days of the date the charge was last incurred, and if it does not, "the billed party is not required to pay the charge." Where the billing party is an NVOCC, its 30-day clock runs from the issuance date of the invoice it received. And under 46 CFR 541.8, the billing party must give the billed party at least 30 calendar days from issuance to request mitigation, refund, or waiver, and must attempt to resolve that request within 30 calendar days of receiving it.
The third is a reasonableness challenge, and it is substantive, so it is hedged to the standard the rule sets. The FMC's interpretive rule, 46 CFR 545.5, says the Commission assesses reasonableness by "the extent to which demurrage and detention are serving their intended primary purposes as financial incentives to promote freight fluidity." It adds that, "absent extenuating circumstances," detention imposed when it does not serve that purpose, "such as when empty containers cannot be returned," is "likely to be found unreasonable." That is a "likely unreasonable" standard, the ground for a mitigation, refund, or waiver request or an FMC charge complaint, not an automatic or promised refund.
A forwarder is often on both sides of these rules. Acting as an NVOCC, it is a billed party when it receives a carrier's or MTO's invoice, and a billing party when it re-bills those charges to its own shipper. When it re-bills, the same rules run the other way: its invoice to the shipper must itself carry the 46 CFR 541.6 required contents, a missing element eliminates the shipper's obligation to pay under 46 CFR 541.5, and its 30-day clock runs from the issuance date of the invoice it received, not from the underlying charge date (46 CFR 541.7).
A currency note, because this surface moves. A separate provision, former 46 CFR 541.4, once specified who a demurrage or detention invoice may be sent to. The U.S. Court of Appeals for the District of Columbia Circuit set that provision aside on 23 September 2025, and it is currently reserved. The FMC states that the rest of 46 CFR Part 541 remains fully applicable, and that it may address who may be invoiced in a future rulemaking. So there is at present no rule limiting who a demurrage or detention invoice may be billed to, and the levers above are unaffected.
These are US rules. Outside US trade, a dispute rests on the carrier's own tariff terms and the contract, not on 46 CFR Part 541.
The free-time allowance, the daily rate, and a carrier's own dispute portal and escalation steps vary by carrier, port, direction, equipment, and contract. Those live in the carrier's tariff and on the per-carrier demurrage and detention pages, which are planned but not yet built. This guide is the cross-carrier framework: the mechanism, and the US billing and dispute rules that apply whoever the carrier is. It names no carrier's free-time number, rate, or dispute channel.
Where Expedion fits (prevention and reconciliation)
Expedion is a managed AI workforce for freight forwarding operations. On demurrage and detention, our surface is the desk work the charges drive, and the dispute itself stays with the billed party. Upstream, exception detection and per-booking cut-off monitoring surface a slipping shipment before its free time runs out and the charge starts to accrue, the same capabilities that run on tracking and booking and against the container shipping cut-offs a missed sailing exposes. Downstream, when an invoice arrives, agents reconcile it against the shipment's own discharge, availability, pickup, and return events and against the invoice's required-data checklist, surfacing a mismatch or a missing required element to the forwarder's reviewer. We do not file the dispute, act as the billed party's advocate, or promise a refund or waiver; the levers above are the billed party's to use. This capability is in supervised production with design partners, not general availability.
Exception detection and per-booking cut-off monitoring flag a slipping shipment while there is still time to act, before free time runs out and demurrage or detention starts to accrue.
Agents check an arriving demurrage or detention invoice against the shipment's own discharge, availability, pickup, and return events and against the invoice's required-data checklist, surfacing a mismatch or a missing required element to the reviewer.
The charge and the dispute belong to the billed party. Expedion prepares and reconciles the data; it does not file the dispute, advocate for the billed party, or promise any outcome.
Frequently asked questions
What is the difference between demurrage and detention?
Both charges begin when a shipment's free time runs out. Demurrage covers a container that stays at the marine terminal past its free time; detention covers the carrier's equipment kept in use after the container leaves the terminal, and in US practice detention is billed as per diem. Per diem is the US billing term for detention, not a separate charge. For the single-term definitions, see the demurrage and detention glossary entries.
How much is demurrage, and who sets the rate?
Demurrage is a carrier-tariff charge, not a rate set by a regulator. It varies by carrier, port, direction, equipment type, and contract, so there is no single figure. The current amount for a given shipment is in that carrier's own tariff table.
How long do I have to dispute a demurrage or detention invoice?
Under the FMC billing rule, 46 CFR 541.8, the billing party must allow the billed party at least 30 calendar days from the invoice issuance date to request mitigation, refund, or waiver, and must attempt to resolve that request within 30 calendar days of receiving it. These are US rules; outside US trade the carrier's tariff and the contract govern.
Can I refuse to pay a demurrage invoice?
Under the FMC rule there are two mechanical cases. If the invoice omits any of the required minimum information (46 CFR 541.5), or if it was issued more than 30 calendar days after the charge was last incurred (46 CFR 541.7), the obligation to pay the charge is eliminated. A substantive challenge, that the charge was unreasonable, goes through a mitigation, refund, or waiver request or an FMC charge complaint on the reasonableness standard in 46 CFR 545.5, which is a likely-unreasonable test, not an automatic refund.
Do the FMC billing rules apply outside the US?
No. 46 CFR Part 541 governs invoices issued by ocean common carriers, marine terminal operators, and NVOCCs for the collection of demurrage or detention charges in US trade. Outside US trade, the carrier's tariff and the contract govern the charge and any dispute.
Does Expedion dispute my charges for me?
No. The charge and the dispute stay with the billed party. Expedion's surface is prevention and reconciliation: exception detection and cut-off monitoring that flag a slipping shipment before free time runs out, and reconciliation of an arriving invoice against the shipment's own discharge, availability, pickup, and return events and its required-data checklist, with any mismatch or missing required element surfaced to the reviewer. It does not file the dispute, act as your advocate, or promise a refund or waiver.