Export & logistics
Container demurrage and detention: what exporters actually owe and when
A held container is one of the most predictable ways a shipment loses money after it has already left the packhouse, and it is also one of the most contested line items on a freight invoice. Demurrage and detention charges accrue quietly, on a clock that starts the moment a vessel discharges cargo, and by the time an exporter or forwarder sees the invoice the dispute window may already be running. For agri-food exporters moving temperature-controlled cargo, the stakes are higher still: a reefer's effective free time is often shorter than a dry box's, and the charges that apply to it are not limited to storage. This guide sets out the precise vocabulary, how free time is actually granted, how per-diem charges escalate, what is specific to reefer equipment, and what US law requires of a demurrage or detention invoice under 46 CFR Part 541, including a legal development from late 2025 that changed part of that rule. Outside the United States, none of the invoicing mechanics below apply; demurrage and detention there are governed by the carrier's own tariff and the contract of carriage, full stop.
Key facts
- Demurrage is the charge for a container held inside the terminal past free time; detention is the charge once the same container is outside the terminal, still with the merchant, past free time; the industry uses per diem inconsistently for both.
- Free time is set by the specific booking or contract, not a universal industry standard, and reefer containers commonly carry shorter effective free time than dry boxes.
- Reefer cargo can accrue plug-in, genset, and cold-chain monitoring charges on top of standard demurrage and detention, billed per day independent of the free-time clock.
- Under 46 CFR 541.6, a US demurrage or detention invoice needs roughly 20 required elements and must be issued within 30 calendar days under 541.7(a); an incomplete or late invoice need not be paid.
- The D.C. Circuit vacated only 46 CFR 541.4 (who may be billed) on 23 September 2025 in World Shipping Council v. FMC; the rest of Part 541 remains fully enforceable, and no replacement rule has been confirmed as of 4 September 2026.
Demurrage and detention are two different charges, not one word
Demurrage is the charge for a container held inside the terminal past its free time: the clock runs from the point the vessel discharges the box and the terminal gates it in, through to the point it is picked up by the merchant or its trucker. Detention is the charge for the same container once it has left the terminal and is in the merchant's possession, past its free time, until it is returned empty to the carrier or its depot. Maersk's own explainer states this distinction directly: demurrage covers time inside the terminal, detention covers time outside it while the equipment is still with the customer.
The industry does not apply this vocabulary consistently. 'Per diem' is used loosely across the trade, often interchangeably with detention, particularly in North American rail and inland contexts, and sometimes as a catch-all for both charge types together. This looseness is a synthesis drawn from trade press rather than a single regulator's definition, so treat the label on any given invoice as a starting point, not a legal conclusion: what actually governs the charge is the specific tariff or contract clause it is billed under, not the word printed on the line item. For an exporter reconciling a freight bill, the practical move is to check whether the charge period sits before or after gate-out, because that boundary, not the vocabulary, is what determines whether you are disputing demurrage or detention.
Both charge types exist because the box is a scarce, carrier-owned asset that the shipping line needs back in circulation. Free time is the grace period before that pressure converts into a daily charge, and how that period is set is the next thing worth understanding precisely, because it is not a fixed industry number.
Free time is contractual, and the clock start point is not universal
Free time, meaning the number of days a container may sit in the terminal or with the merchant before daily charges begin, is granted by the carrier or terminal as a term of the specific booking, service contract, or tariff in force, not as a fixed industry-wide allowance. Two shipments on the same trade lane, even with the same carrier, can carry different free-time allowances depending on the negotiated contract, the port, and the equipment type. This is why an exporter cannot assume the free time quoted on a prior shipment will carry over to the next one: it needs to be confirmed on the booking or service contract in force for that specific move.
The start and end points of the free-time clock are similarly contract-specific rather than universal. For an import move, the clock typically starts from vessel discharge or container availability and runs until the container is picked up (demurrage) or, after pickup, until it is returned empty (detention). For an export move, the relevant date is the earliest return date, the point from which the exporter's container becomes chargeable if it is not delivered back empty in time. Because these start and stop points are set by tariff language rather than a universal rule, a dispute over whether a charge applies almost always comes down to reading the specific contract or tariff clause the invoice cites, which is exactly why the invoicing requirements covered later in this guide matter: a compliant US invoice under 46 CFR 541.6 has to state the free-time start date, the free-time end date, and the specific dates being charged, in writing, on the document itself.
Booking free time correctly against realistic cargo-clearance and pickup timelines, well before the vessel arrives, does more to avoid demurrage and detention than anything else an exporter or forwarder can do later. Getting that estimate wrong is compounded by the fact that charges do not simply accrue at a flat daily rate once free time expires; they typically escalate.
Per-diem tiering: the daily rate rises the longer the box is held
Demurrage and detention charges commonly escalate in tiered bands the longer a container sits past its free time: a lower per-day rate applies for the first few days beyond expiry, then a higher rate kicks in for a second band, and a higher rate again for a third. This tiered structure is widely reported in trade press, with ports such as Los Angeles and Long Beach cited as examples, but the exact number of bands, the day-ranges they cover, and the dollar figures attached to them vary by carrier, port, and contract, and no single verified carrier tariff document was confirmed in this research pass. Treat any specific per-day figure you see quoted online as illustrative rather than a number to plan a budget around; the only reliable source for the actual bands on a given shipment is that carrier's or terminal's own current tariff.
The practical consequence for an exporter is that the cost of a delay is not linear. A container held five days past free time does not cost five times the first day's rate; it can cost meaningfully more once it crosses into a second or third tier, because the daily rate itself has stepped up. This makes early awareness of a looming delay, whether from customs holds, congestion, or a missing document, disproportionately valuable relative to the same delay discovered late, since the earlier days of any overage sit in the cheapest tier and the later days sit in the most expensive one.
Tiering interacts with reefer cargo in a way dry cargo does not experience, because a temperature-controlled container is not simply sitting idle while it accrues demurrage or detention. It is also, in many cases, running.
Reefer specifics: why a plugged-in container still costs money every day
Reefer containers commonly carry shorter effective free time than dry containers, often reported as under seven days versus roughly seven to fourteen days for a standard dry box. This is trade-press and industry synthesis rather than a single regulator's figure, but the underlying logic is consistent across sources: ports and carriers pass through the cost and complexity of continuous power and monitoring, reefer equipment is scarcer within a carrier's fleet than dry equipment, and the spoilage risk on temperature-sensitive cargo creates pressure, from all sides, to move the box quickly. Confirm the actual free-time allowance on the specific booking rather than assuming a shorter reefer window applies universally.
Beyond standard demurrage and detention, reefer cargo can attract charges that dry cargo never sees: a plug-in or power fee for keeping the unit connected and running at the terminal, genset rental for a portable generator when the box moves by road or rail without fixed power available, and cold-chain monitoring fees for data loggers tracking temperature and location in transit. These are industry-standard practice rather than a single universal tariff line, and at least one major carrier, OOCL, publishes a named category on its own local-information page for 'Demurrage and Detention Free Time Costs and Reefer Monitoring Charges', which corroborates that reefer monitoring is billed as a distinct line separate from standard demurrage and detention on at least one carrier's tariff information. That page could not be independently fetched in this research pass, so the exact figures on it are unconfirmed; do not treat any specific EUR or USD rate you encounter elsewhere as a current, verified tariff.
The point worth internalising is that a reefer accrues cost even while it is plugged in and, from a spoilage standpoint, perfectly safe: the plug-in and monitoring charge is billed per day independent of whether the container is still inside its demurrage-free window, so a temperature-controlled shipment can be paying storage charges and power or monitoring charges at the same time. That stacking, combined with a shorter effective free-time window, is the single biggest reason reefer-heavy exporters should treat demurrage and detention exposure as a distinct cost line to manage actively rather than a rare exception, an idea covered further in cold storage for exporters and in the record-keeping discipline set out in cold chain record keeping.
What US law actually requires on a demurrage or detention invoice
In the United States, the Federal Maritime Commission's rule at 46 CFR Part 541, titled Demurrage and Detention Billing Requirements, sets out what a compliant invoice must contain and how quickly it must be issued and disputed. The rule was published in the Federal Register on 26 February 2024 as document 2024-02926, with the bulk of the rule taking effect on 28 May 2024; two of its sections, 541.6 (invoice contents) and 541.99 (the companion Paperwork Reduction Act control-number section, OMB Control No. 3072-0073, approved 16 April 2024), were held back pending OMB approval and came into force together with the rest of the rule on that same 28 May 2024 date.
The statutory foundation underneath the rule, 46 U.S.C. 41104(d)(2), lists exactly thirteen required invoice elements, lettered (A) through (M): the date the container was made available, the port of discharge, the container number(s), the earliest return date for exports, the number of days of allowed free time, the free-time start date, the free-time end date, the applicable demurrage-or-detention rule the rate is based on, the applicable rate(s), the total amount due, contact information for questions or mitigation requests, a statement confirming compliance with FMC rules, and a statement that the carrier's own performance did not cause or contribute to the charges. The FMC's implementing rule at 46 CFR 541.6 builds on that statutory floor with roughly seven further data elements, covering items such as the bill of lading number, the container-availability date, the basis for the billed party's liability, a digital or URL-based dispute mechanism, and defined dispute timeframes, bringing the total to approximately twenty distinct elements across five lettered subsections addressing identifying information, timing, rate, dispute process, and certifications.
Two firm deadlines sit alongside those content requirements. Under 46 CFR 541.7(a), the billing party must issue the invoice within 30 calendar days of the date the last charge was incurred, with a similar 30-day window applying to an NVOCC passing charges on from receipt. Under 46 CFR 541.8(a), the billing party must then give the billed party at least 30 calendar days from the invoice date to request mitigation, a refund, or a waiver, and to attempt dispute resolution, unless the parties have separately agreed to different terms. Both the FMC's own summary of the rule and the statute itself, at 46 U.S.C. 41104(f), are direct on the consequence of getting either of these wrong: a billed party is not obligated to pay a demurrage or detention charge if the invoice omits any required 541.6 element, is inaccurate, or was not issued within the 30-day window. That non-payment defense is the single most useful fact in this guide for an exporter or forwarder who receives a disputed charge, because it means the first check on any demurrage or detention invoice should be a line-by-line audit against the 541.6 checklist and the 30-day clock, not a negotiation over the rate itself.
A late-2025 court decision narrowed one part of the rule, not all of it
The World Shipping Council petitioned for review of the final rule in the US Court of Appeals for the District of Columbia Circuit, docketed as World Shipping Council v. FMC, No. 24-1088, arguing the rule was arbitrary and capricious and contrary to the Ocean Shipping Reform Act of 2022 under the Administrative Procedure Act. The court's own signed opinion records the case as argued on 13 March 2025 and decided on 23 September 2025. We could not confirm the petition's filing date from any source that actually states it, so this guide does not give one.
On 23 September 2025, the D.C. Circuit decided the case. The court vacated and set aside only one provision, 46 CFR 541.4, the 'who may be billed' rule that had limited invoicing to the party who contracted with the billing party for ocean transportation or storage, or the consignee. The court found the FMC had not adequately explained why motor carriers were excluded from being billed while consignees were included. Every other part of Part 541 was left intact as severable and remains fully enforceable: the 30-day issuance deadline, the 30-day dispute window, and the invoice-content requirements in 541.6, 541.7 and 541.8 all still apply exactly as described above. A Federal Register document formally implementing the removal of 541.4 from the Code of Federal Regulations, titled Demurrage and Detention Billing Requirements; Properly Issued Invoices Provision Set Aside by Court (document 2025-23920), carries a stated effective date of 29 December 2025.
As of this research pass on 4 September 2026, no evidence was found of the FMC having opened a replacement rulemaking on the 'who may be billed' question. The FMC's own article on the court decision, published 20 November 2025, states that the decision 'does not preclude the Commission from addressing who may be invoiced for demurrage and detention in a future rulemaking' and notes the court suggested the FMC 'might elect to maintain the same policy... so long as it provides a fuller explanation of its reasons.' That language commits to no timeline and names no docket, and it remains the most recent public FMC statement on the topic found in this research. This should be read as an open question rather than a confirmed absence of activity: the lack of a public announcement between January and September 2026 is not proof that nothing has moved internally at the Commission. An exporter or forwarder relying on this guide should treat the identity of who can lawfully be billed for demurrage and detention as currently unsettled by regulation, while the content, timing and dispute mechanics of any invoice issued to them remain governed exactly as 541.6 through 541.8 describe.
What you can actually contest, and how
Given the framework above, an exporter, packhouse, or forwarder disputing a US demurrage or detention charge has a specific, checkable set of grounds rather than a general appeal to fairness. First, check the invoice date against the last date a charge was incurred: if more than 30 calendar days separate the two, the invoice was issued late under 46 CFR 541.7(a) and the billed party has no payment obligation on it. Second, work through the roughly twenty required elements in 46 CFR 541.6, the bill of lading and container numbers, the free-time start and end dates, the specific dates charged, the applicable rate and rule citation, and the required certifications, and flag any that are missing or wrong; an incomplete or inaccurate invoice carries the same non-payment consequence as a late one, under both the FMC's rule summary and 46 U.S.C. 41104(f) directly. Third, once a dispute is raised, the billing party must give at least 30 calendar days from the invoice date to pursue mitigation, refund, or waiver under 46 CFR 541.8(a), so a request made within that window should be formally acknowledged and addressed, not simply ignored.
Outside these procedural grounds, the substantive question of whether the free time itself was reasonable, whether a port congestion event or a customs hold beyond the merchant's control caused the delay, or whether the carrier's own performance contributed to the overage, is where the certification in 541.6(e) becomes relevant: the billing party must state that its own performance did not cause or contribute to the charges, which gives a billed party a documented basis to challenge a charge where equipment availability, vessel delay, or terminal congestion on the carrier's side was the actual cause of the overage rather than any failure on the merchant's part.
None of this applies once cargo moves outside the United States. Outside the US, demurrage and detention are governed purely by the carrier's own tariff and the contract of carriage in force for that shipment; there is no equivalent regulator, and no equivalent statutory invoice-content or timing mandate, in any jurisdiction checked for this guide. For a non-US move, the operative discipline is the same one this guide opened with: confirm the free-time allowance and its start and stop points in writing on the booking or service contract before the vessel sails, because there is no regulatory floor standing behind the invoice if it arrives late, incomplete, or wrong.
Sources
- Federal Register, Demurrage and Detention Billing Requirements (Final Rule, 2024-02926)Checked 2026-09-04
- Cornell LII, 46 CFR 541.6Checked 2026-09-04
- GovInfo, CFR 2025 Title 46 Vol 9, Part 541 (XML)Checked 2026-09-04
- Cornell LII, 46 U.S.C. 41104Checked 2026-09-04
- FMC, FMC Publishes Final Rule on Detention and Demurrage Billing PracticesChecked 2026-09-04
- FMC, Final Rule on Demurrage/Detention Cleared to Take Full Effect May 28Checked 2026-09-04
- FMC, U.S. Court of Appeals Issues Decision in Case on Demurrage and Detention Billing PracticesChecked 2026-09-04
- US Court of Appeals for the DC Circuit: World Shipping Council v. FMC, No. 24-1088, signed opinion (PDF)Checked 2026-09-04
- Federal Register, Properly Issued Invoices Provision Set Aside by Court (2025-23920, eff. 29 December 2025)Checked 2026-09-04
- Maersk, What is demurrage and detention in shipping for buyers?Checked 2026-09-04
- Holland and Knight, FMC Announces Demurrage and Detention Final RuleChecked 2026-09-04
- Federal Register: Demurrage and Detention Billing Requirements, effective-date notice (89 FR 42128, 14 May 2024) recording OMB approval of control number 3072-0073 on 16 April 2024Checked 2026-09-04
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