Demurrage and Detention Billing: FMC Rules and Dispute Guide

Every container that lingers past its allotted free time generates one of two types of charges, and confusing them is one of the most common mistakes in international shipping. The distinction matters because each charge type has different responsible parties, different rate structures, and different dispute pathways under federal regulation.

Demurrage applies when a loaded container remains at the port terminal beyond the free time period granted by the ocean carrier or marine terminal operator. Free time typically ranges from three to seven calendar days after a container is discharged from the vessel, though the exact window depends on the carrier's tariff and the specific terminal. Once that window closes, demurrage accrues daily. These charges compensate the terminal for occupied yard space and are meant to incentivize prompt container pickup. Demurrage is distinct from port storage charges, which some terminals assess separately for use of their facilities; in practice, the two are sometimes bundled on a single invoice, making line-item verification essential.

Detention kicks in once a container leaves the terminal. If an importer or consignee holds an empty container at their warehouse, distribution center, or any off-terminal location beyond the allowed return period, detention charges accumulate until the box is returned to a designated depot. Detention compensates the carrier for lost use of their equipment.

Per diem is where terminology gets muddled. Some carriers use "per diem" interchangeably with detention. Others apply it specifically to chassis rental fees when a container's chassis is held beyond its own free time allowance, separate from the container itself. When reviewing invoices, do not assume "per diem" means the same thing across carriers. Check the tariff schedule to confirm exactly what the charge covers.

Some carriers also assess combined D&D charges, where the detention clock begins running on the date of container pickup even though demurrage was accruing up to that point. In these arrangements, a container that has exceeded free time on both counts faces a substantially higher total daily cost than either charge alone. Check your carrier's tariff to understand whether they bill demurrage and detention separately or in combination.

The financial exposure from demurrage and detention billing is significant. Rates typically start at $100 to $150 per container per day during the first tier and escalate sharply, often reaching $300 to $500 or more per day as containers sit longer. Tiered rate structures mean that a container held ten days past free time can cost several times more per day than one held two days past. Across the industry, these charges add up to enormous sums. Nine major ocean carriers collected roughly $15.4 billion in demurrage and detention charges between April 2020 and March 2025, with the amount billed increasing approximately nine-fold between Q2 2020 and Q1 2022, according to FMC detention and demurrage data. Those numbers underscore why accurate demurrage and detention invoice processing is not optional for importers managing containerized cargo.

The Federal Maritime Commission recognized this financial pressure and responded with 46 CFR Part 541, a Final Rule establishing specific billing requirements for D&D invoices. Under the rule, carriers and marine terminal operators must issue invoices within 30 calendar days of when the charge was incurred. Each invoice must contain defined data elements, including the container number, the dates used to calculate free time, the applicable rate, and identification of the billing and billed parties. The regulation carries real teeth: if a D&D invoice fails to include the required information, the billed party has no obligation to pay. That single provision fundamentally shifted the power dynamic between carriers and importers.

The regulatory framework has continued to evolve. The FMC's 2024 Final Rule established the billing requirements, and a September 2025 D.C. Circuit court ruling modified the scope of certain provisions. The sections that follow reflect the current regulatory state after that ruling, covering exactly what the rule requires, what the court changed, and how to verify and dispute D&D invoices under the framework as it stands now.

FMC Billing Requirements Under 46 CFR Part 541

The Ocean Shipping Reform Act of 2022 (OSRA 22) gave the Federal Maritime Commission a clear mandate: fix demurrage and detention billing practices that had burdened importers with vague, unverifiable charges for years. The FMC responded with a Final Rule codified at 46 CFR Part 541, which took effect on May 28, 2024. This regulation establishes specific data elements that every D&D invoice must contain, sets a hard deadline for invoice issuance, and creates enforceable consequences when billing parties fail to comply.

Required Data Elements

Under Part 541, a compliant demurrage or detention invoice must include all of the following:

Container number(s) subject to the charge
Date range over which charges accrued
Applicable rate per container per day
Free time calculation, including the start date, end date, and the basis used to determine the free time allowance
Total charges assessed
Billing party identification and contact information, including a point of contact for invoice inquiries and dispute filing
Identification of the entity being billed

Each element serves a verification purpose. Without the container number and date range, you cannot cross-reference the invoice against your own terminal or port records. Without the rate and free time calculation, you have no way to confirm the math. Without clear billing party contact information, you have no channel to challenge errors.

The 30-Day Issuance Rule

Part 541 imposes a strict timing requirement: D&D invoices must be issued within 30 calendar days of the date on which the charges were last incurred. An invoice that arrives on day 31 or later is non-compliant on its face, regardless of whether the underlying charges were otherwise legitimate. This prevents the longstanding practice of carriers and terminals sending invoices weeks or months after the fact, when importers no longer have easy access to the records needed to verify them.

Consequences of Non-Compliance

This is the provision that carries the most practical weight for importers, and one that many are still unaware of. Under Section 541.7, if a D&D invoice fails to include the required data elements, the billed party's payment obligation is eliminated. Not reduced. Not deferred. Eliminated.

This is not a technicality buried in regulatory footnotes. It is a deliberate enforcement mechanism designed to shift the compliance burden onto billing parties. If you receive a demurrage or detention invoice that omits the free time calculation, leaves off the per-day rate, or lacks the billing party's contact information for disputes, you are under no legal obligation to pay that invoice under federal regulation.

Who Must Comply

The FMC billing requirements under 46 CFR Part 541 apply to ocean common carriers, marine terminal operators, and their agents. Whether you receive a D&D invoice directly from a carrier, from a terminal operator, or from a third party billing on their behalf, the same data element and timing requirements apply. There is no exemption based on the size of the billing party or the volume of containers involved.

For importers, customs brokers, and freight forwarders on the receiving end of these invoices, Part 541 provides a concrete checklist. Every invoice that crosses your desk should be measured against it before any payment is approved.

What the 2025 D.C. Circuit Ruling Changed

When the FMC finalized its demurrage and detention billing rule in February 2024, Section 541.4 was one of its most consequential provisions. It restricted who could receive a D&D invoice to two categories: the consignee listed on the bill of lading, or the contracting party holding the billing account with the ocean carrier or marine terminal operator. No other entity could be billed. For importers and brokers, this created a clear boundary around billing exposure.

That restriction no longer exists.

In September 2025, the D.C. Circuit Court of Appeals ruled in World Shipping Council v. FMC that Section 541.4 was "arbitrary and capricious." The court found that the FMC had not adequately justified limiting which parties could be billed for demurrage and detention charges. The World Shipping Council, representing major ocean carriers, had challenged the provision on the grounds that it interfered with existing contractual relationships and commercial practices across the supply chain. The court agreed and vacated the section entirely. By December 2025, the FMC had formally removed Section 541.4 from the Code of Federal Regulations.

What remains in force. The court's ruling was narrow. It struck down only the billing party restriction. The rest of 46 CFR Part 541 survived intact:

Section 541.3 — The 30-day issuance window. Carriers and MTOs must issue D&D invoices within 30 calendar days of the charge being incurred.
Section 541.6 — Content requirements. Every invoice must include the specific line items, dates, applicable tariff references, and other disclosures outlined in the rule.
Section 541.7 — Payment obligation elimination. If an invoice fails to comply with the content requirements, the billed party has no obligation to pay.
Section 541.8 — Dispute resolution provisions. Billed parties retain the right to challenge invoices, and billing parties must respond within defined timeframes.

The practical effect is significant. Carriers and marine terminal operators are no longer restricted in who they can bill for D&D charges. Freight forwarders, trucking companies, NVOCCs, and other supply chain participants who were previously outside the billing scope may now receive D&D invoices directly. For customs brokers managing D&D on behalf of clients, this widens the universe of entities that might forward invoices seeking payment or reimbursement.

A note on outdated guidance. Most publicly available D&D billing guides, law firm client alerts, and carrier FAQ pages were written in early 2024, shortly after the original rule took effect. Many still reference Section 541.4's billing party restrictions as current law. If you are relying on any external guidance for D&D billing compliance, check whether it accounts for the September 2025 court decision and the December 2025 regulatory update. Any source that still describes the consignee-or-contracting-party limitation as binding is out of date.

How to Verify a Demurrage or Detention Invoice

A D&D invoice sitting on your desk is not a final verdict. Carriers and terminals make billing errors more often than most importers realize, and paying without verification means absorbing costs you may not legally owe. The following verification process works for any demurrage or detention invoice, whether from an ocean carrier, marine terminal operator, or intermodal equipment provider. If your team is tightening controls across all carrier bills rather than port charges alone, a broader freight audit and payment process for shippers helps connect D&D review to rate checks, duplicate-charge controls, and AP approval rules.

Step 1: Verify the Free Time Calculation

Pull the applicable tariff or service contract and confirm the free time period granted for the specific terminal and container type. Standard free time typically runs 3 to 5 calendar days for demurrage and 4 to 7 days for detention, but contracted terms frequently differ from published tariffs.

Check three things against the invoice:

The start date of free time. Free time begins when the container becomes available for pickup, not when the vessel arrives or berths. The container availability date and the vessel discharge date are often different by one or more days.
The last free day. Count forward from the availability date using the number of free days granted. Confirm whether the terminal calculates free time using calendar days or business days, as this varies by facility and directly affects when charges begin accruing.
The charge start date. Charges should begin the day after the last free day expires. If the invoice shows charges starting earlier, the free time calculation is wrong.

To illustrate: a container becomes available for pickup on Monday, March 3, with five calendar days of free time. The last free day is Saturday, March 8, and demurrage charges begin Sunday, March 9. But if the terminal's tariff excludes weekends, those two weekend days do not count toward free time, pushing the last free day to Wednesday, March 12, and charges to Thursday, March 13. That four-day difference could represent $400 to $2,000 in charges depending on the rate tier.

Step 2: Check Holiday and Weekend Exclusions

Not all terminals treat non-business days the same way. Some exclude weekends and federal holidays from the free time calculation, effectively extending your window. Others count every calendar day regardless.

The governing document is the specific terminal's tariff, not a blanket industry standard. If a terminal was closed on a federal holiday and that day falls within your free time window, check whether the tariff excludes that day. An invoice that counts a terminal-closed holiday as a chargeable day when the tariff excludes it is billing you incorrectly.

Step 3: Confirm Container Event Timestamps

Timestamp discrepancies are among the most common sources of D&D billing errors. Pull your own records and cross-reference four critical dates against what the invoice states:

Vessel discharge date — when the container was offloaded from the ship
Container availability date — when the container was actually available for pickup (often later than discharge due to customs holds or terminal processing)
Container pickup date — when the trucker retrieved the container from the terminal (relevant for demurrage)
Container return date — when the empty container was returned to the designated depot or terminal (relevant for detention)

Compare these against terminal gate-in and gate-out records, carrier tracking data, and your own dispatch logs. Even a one-day discrepancy in the availability or pickup date can shift the entire billing calculation, particularly when tiered rates apply.

Step 4: Validate the Applied Rate

Container detention charges and demurrage rates rarely stay flat across the billing period. Most carriers and terminals use escalating tier structures where the daily rate increases the longer the container is held. A typical structure might charge $75 per day for days 1 through 4 past free time, $150 for days 5 through 8, and $250 per day beyond that.

Verify two things:

The base rate matches your contract or the published tariff. If you have a service contract with negotiated D&D rates, those rates govern rather than the carrier's standard tariff. Invoices sometimes default to published rates even when a contract rate exists.
The correct tier was applied for each day. Count the chargeable days and confirm that each day falls within the right rate tier. An invoice that applies the highest tier rate from day one when it should be using a graduated scale will significantly overstate the amount owed.

Step 5: Check for Charges After Container Return

One of the most frequent detention billing errors is the continuation of charges after the container has already been returned. If your gate-out records or depot receipts confirm the empty was returned on a specific date, no detention charges should accrue beyond that date.

This error often results from delays in the carrier's system reflecting the return transaction. The depot may have accepted the container, but the carrier's billing system may not update for several days. When you spot post-return charges, the gate receipt or interchange document from the return facility is your primary evidence for contesting them.

Step 6: Cross-Reference Against 46 CFR Part 541 Content Requirements

Even if the dollar amounts on the invoice are accurate, the invoice itself may fail to meet federal content requirements. Under 46 CFR Part 541, D&D invoices must include specific data elements such as the billing party's identity, the container number, the dates used in the calculation, the applicable rate, and the total amount assessed.

If any required element is missing, the invoice may be unenforceable regardless of whether the underlying charges are correct. This is a distinct issue from mathematical accuracy. An invoice can show the right number of days and the right rate but still fail to create a valid payment obligation if it omits a mandated data field.

Review each invoice against the Part 541 requirements before making payment decisions. For organizations handling high volumes of D&D invoices, automating freight invoice data extraction can systematically flag missing fields and timestamp discrepancies that manual review might miss.

Filing a D&D Invoice Dispute Under Federal Regulation

When a demurrage or detention invoice contains errors, inflated charges, or billing for periods outside your control, federal regulation gives you a structured path to challenge it. Knowing the valid grounds, the documentation you need, and the procedural timelines transforms a frustrating billing dispute into a methodical process with regulatory backing.

Valid Grounds for Disputing D&D Charges

Not every high invoice warrants a formal dispute, but several categories of charges are clearly contestable under current FMC rules:

Charges accrued beyond the billed party's control. This is the most consequential category. If demurrage or detention accumulated because of terminal congestion, equipment unavailability, appointment system failures, or government holds and inspections, the billed party has strong grounds to challenge those charges. The FMC has repeatedly emphasized that carriers and marine terminal operators cannot penalize shippers for delays the shipper did not cause.

Invoices missing required data elements. Under 46 CFR Part 541, every D&D invoice must include specific information — container numbers, free time start and end dates, applicable rates, and the identity of the billing and billed parties, among other fields. An invoice that omits required elements is non-compliant, and non-compliant invoices are disputable on procedural grounds alone.

Rate discrepancies. If the per-diem rate on the invoice does not match the rate published in the carrier's tariff or specified in your service contract, that discrepancy is a clear basis for dispute. Pull your contract or the carrier's publicly filed tariff and compare line by line.

Billing for dates after container return. Detention charges should stop accruing once the container is returned to the designated facility. If the invoice includes charges for dates after your gate-in timestamp, those charges are erroneous.

Incorrect free time calculation. Verify that the free time period was calculated correctly from the actual vessel discharge date, not from an earlier estimated arrival. Even a one-day error in free time calculation can result in thousands of dollars in unwarranted charges across multiple containers.

Documentation to Gather Before Filing

A dispute without supporting evidence is unlikely to succeed. Before initiating any formal challenge, assemble the following records:

Container tracking records showing the full movement history of each disputed container
Terminal gate-in and gate-out timestamps proving when containers were picked up and returned
Appointment booking confirmations and any records of appointment unavailability or cancellations by the terminal
Vessel discharge dates from the bill of lading or terminal records, which establish when free time actually began
Chassis availability records for detention disputes where equipment shortages prevented timely container return
Terminal congestion notices or port advisories that support force majeure arguments for periods when pickup or return was physically impossible
The carrier's tariff or service contract for rate verification against invoiced amounts

Organize this documentation chronologically, container by container. A well-organized dispute package with clear evidence dramatically increases the likelihood of a favorable resolution and shortens the review timeline.

Dispute Timeline Under the FMC Rule

The FMC's billing rule establishes a defined process with enforceable deadlines. Here is how it works in practice:

Step 1: Request a billing review. The billed party submits a written request to the billing party (the carrier or marine terminal operator) identifying the specific charges in dispute, the grounds for the dispute, and the supporting documentation. There is no mandated format, but a clear, itemized request referencing specific container numbers and date ranges will be processed faster than a general objection.

Step 2: The billing party must respond within 30 calendar days. Once the billing party receives the dispute request, they are required to attempt resolution within 30 days. This is not optional — the 30-day window is a regulatory obligation, not a courtesy timeline.

Step 3: If the dispute is denied, the billing party must explain why. A blanket denial is insufficient. The billing party must provide a detailed written explanation of the denial, including the specific grounds for rejecting each disputed charge. This requirement prevents carriers from stonewalling disputes with form-letter rejections and creates a documented record that becomes valuable if you escalate.

Escalation to the FMC

If the direct dispute process fails to produce a satisfactory resolution, you are not out of options. Importers, customs brokers, and freight forwarders can file a formal complaint with the Federal Maritime Commission under 46 U.S.C. § 41301.

The FMC complaint process allows the Commission to investigate whether the disputed charges violated the Shipping Act. This includes examining whether charges were applied in a manner that was unjust or unreasonable, whether the billing party complied with the procedural requirements of 46 CFR Part 541, and whether the billing party engaged in prohibited practices such as refusing to negotiate or failing to provide the required written denial.

If the FMC finds violations, it has the authority to order reparations — meaning the carrier or terminal operator can be required to refund overcharges. The formal complaint process involves filing fees and typically takes several months, but it provides a binding resolution backed by federal enforcement authority. For disputes involving large sums across multiple containers, the FMC complaint route is a legitimate and well-established recourse.

The National Shipper Advisory Committee

The National Shipper Advisory Committee is an FMC advisory body composed of industry representatives who provide recommendations on shipping practices, including D&D billing. Their advisory opinions are not legally binding, but they carry practical weight: citing a relevant recommendation in your dispute demonstrates that your position aligns with evolving regulatory thinking on reasonable billing practices. The Committee's work also influences future FMC rulemaking and enforcement priorities, making their published advisories worth monitoring for early signals on which billing practices face increased scrutiny.

Strategies to Reduce Demurrage and Detention Costs

Verification and dispute provide recourse after charges accrue, but the strongest financial position is preventing those charges from materializing in the first place. The following strategies target the root causes of D&D exposure through better contracts, tighter operations, and proactive container management.

Negotiate Extended Free Time in Carrier Contracts

Standard free time allocations from ocean carriers — typically three to five days for demurrage and four to seven days for detention — assume a supply chain that moves with minimal friction. That assumption rarely holds. Customs clearance delays, inland transport scheduling, warehouse receiving windows, and chassis availability all consume free time before cargo even leaves the port area.

When negotiating or renewing ocean carrier service contracts, treat free time as a primary commercial term rather than an afterthought. Specific tactics include:

Request trade-lane-specific free time based on actual dwell time data for each port pair. A shipment clearing through a congested gateway port needs more buffer than one arriving at a less trafficked facility.
Negotiate separate demurrage and detention free time rather than accepting a combined allowance. The operational triggers for each charge type are different, and a combined window often proves inadequate for both.
Link free time to volume commitments. Carriers are more willing to extend free time for shippers who guarantee consistent container volumes across a contract year.
Include force majeure and congestion provisions that automatically extend free time during port disruptions, labor actions, or declared emergency periods.

Extended free time reduces D&D exposure at the source and is one of the highest-leverage negotiation points available in carrier contracts.

Use Pre-Pull and Transloading Strategies

When operational realities make it impossible to pick up and return containers within free time, two logistics strategies can break the cost cycle.

Pre-pulling moves containers out of the marine terminal and into a nearby off-dock warehouse or container yard before demurrage free time expires. This eliminates demurrage charges entirely, though detention continues to accrue until the empty container is returned to the carrier. The economics work when demurrage rates exceed the cost of the pre-pull drayage move plus temporary storage — a calculation that increasingly favors pre-pulling as carrier per-diem rates climb.

Transloading takes the approach further. Cargo is stripped from the ocean container at a cross-dock facility and loaded directly onto domestic trucks or equipment. The empty ocean container is returned to the carrier immediately, eliminating both demurrage and detention. Transloading is particularly effective for:

Shipments destined for inland locations where round-trip container return times would exceed detention free time
High-value cargo where D&D charges per container would significantly exceed transloading costs
Peak season periods when terminal congestion makes timely pickup unreliable

Weigh the per-container cost of pre-pull or transloading against the D&D charges each strategy avoids. For many importers, the break-even point arrives sooner than expected.

Optimize Terminal Appointment Systems

Terminal appointment systems are a frequent source of avoidable D&D charges. Pickup slots fill quickly at congested ports, and importers who cannot secure timely appointments watch free time expire while their containers sit on the terminal.

Book pickup appointments as early as possible after vessel discharge. Many terminals open appointment windows 48 to 72 hours before vessel arrival. Monitoring vessel tracking data and booking slots preemptively — before the freight availability notice arrives — gives you first access to available windows.

Maintain backup plans for congested periods. Identify alternative terminals, off-peak pickup windows, and secondary drayage providers who can execute pickups on short notice. During peak seasons, a single missed appointment can cascade into days of additional charges.

Document every appointment attempt and every instance of unavailability. Screenshot the appointment portal showing no available slots. Save confirmation emails for appointments that were canceled by the terminal. Record the dates, times, and outcomes of each attempt. This documentation is not optional — it forms the evidentiary foundation for disputing D&D charges that accrued because the terminal, not the importer, prevented timely container retrieval. Under FMC regulations, charges resulting from circumstances outside the billed party's control are contestable, but only with contemporaneous proof.

Implement Real-Time Container Tracking

Shifting D&D management from reactive invoice processing to proactive prevention requires visibility into where every container sits relative to its free time clock. Real-time container tracking — through carrier portals, terminal operating system APIs, or third-party visibility platforms — enables logistics teams to:

Monitor free time expiration dates across the entire active container portfolio, not just individual shipments
Trigger pickup or return actions before charges begin, rather than discovering accrued charges on an invoice weeks later
Identify at-risk containers early enough to deploy pre-pull, transloading, or expedited drayage before the cost curve steepens
Compare actual dwell times against contractual free time to validate whether carrier invoices reflect the correct charge start dates

The operational value compounds with import volume. An importer managing dozens of containers per week across multiple ports cannot rely on manual spreadsheet tracking to catch every free time expiration. Automated alerts and dashboard visibility turn D&D cost management into a systematic process rather than a reactive scramble.

Establish Internal D&D Monitoring Processes

Technology alone does not reduce D&D costs without organizational discipline behind it. Building a structured internal process ensures that container management receives consistent attention rather than sporadic firefighting.

Assign clear ownership. Designate a specific role or team responsible for D&D management within the logistics or supply chain organization. When responsibility is diffused across dispatchers, brokers, and warehouse staff, containers fall through the cracks.

Set up automated alerts for containers approaching free time expiration — ideally at 48 hours remaining, 24 hours remaining, and at expiration. Each alert should trigger a defined action: confirm pickup appointment, initiate pre-pull, or escalate to management.

Track D&D costs systematically by carrier, terminal, trade lane, and root cause. This data reveals patterns that inform future decisions:

Which carriers consistently generate the highest D&D charges, and whether renegotiating their contracts or shifting volume would reduce costs
Which terminals create the most appointment-related delays, warranting pre-pull arrangements or alternative routing
Which trade lanes have structural free time shortfalls that need contractual adjustment

Importers using European trade lanes face additional complexity beyond D&D charges. Each country layers on distinct maritime invoicing requirements in international shipping, and understanding these obligations alongside D&D billing helps build a more complete compliance framework across your port network.

Quarterly reviews of D&D cost data, combined with carrier scorecards and terminal performance metrics, transform what many organizations treat as an unavoidable cost of importing into a manageable, reducible expense category.