Demurrage and Detention: FMC Billing Rules and Disputes

Container charges pile up fast when a box sits at the terminal or the empty comes back late. Since 2024 federal rules control what those invoices must say and when they must be sent, and a bad invoice may not have to be paid at all.

What the charges are

Ocean carriers and terminals give a set number of free days to pick up an import container and to return the empty, or to deliver an export. After free time, charges start, usually per container per day and often rising the longer it goes on. The terms are used loosely in the industry, so the table shows the common meaning, not a legal rule.

Charge	Common meaning	Clock usually runs while	Who usually bills
Demurrage	Use of terminal space by a container or cargo past free time	The full container sits at the terminal	Ocean carrier or marine terminal operator
Detention	Use of the carrier's container outside the terminal past free time	The box is out on the road or at the customer, until the empty is returned	Ocean carrier or NVOCC
Per diem	Daily equipment use charge, often billed to the trucker under the interchange agreement	The trucker has the box or chassis	Equipment provider

The federal rule defines demurrage or detention broadly: any charge, including per diem, related to the use of terminal space or shipping containers, other than freight charges. Do not confuse these with truck detention, which is what a trucker charges a shipper for waiting at a dock; that is covered in detention and accessorials.

The legal framework

Ocean Shipping Reform Act of 2022

The Ocean Shipping Reform Act of 2022 was enacted on June 16, 2022. For demurrage and detention it did three things that matter to small shippers and truckers. It directed the FMC to set rules on what demurrage and detention invoices must contain. It created a charge complaint process, now at 46 U.S.C. 41310, that lets anyone submit a charge to the FMC for investigation. And in those cases it put the burden on the carrier to show that the demurrage or detention charge was reasonable, not on the shipper to prove it was not.

The FMC billing rule (46 CFR Part 541)

The FMC published its final rule on demurrage and detention billing on February 26, 2024 (89 FR 14362). It took effect on May 28, 2024. Part 541 applies to demurrage and detention invoices issued by ocean common carriers, marine terminal operators and NVOCCs. It does not govern billing between carriers and terminal operators.

What changed in 2025

The rule originally included a section, 46 CFR 541.4, that limited who could be invoiced, which kept motor carriers from being billed. On September 23, 2025, the US Court of Appeals for the D.C. Circuit set aside that one section in a challenge brought by the World Shipping Council. The FMC removed it from the regulations effective December 29, 2025. The FMC has stated that the rest of Part 541 remains in effect, including the invoice content requirements and the 30-day issuance deadline.

What every invoice must contain

Under 46 CFR 541.6, a demurrage or detention invoice must include at least the following. Missing any of it eliminates the billed party's obligation to pay that charge.

Category	Required information
Identification	Bill of lading number(s); container number(s); for imports, the port(s) of discharge; the basis for why the billed party is the proper party of interest
Timing	Invoice date; due date; allowed free time in days; start and end date of free time; for imports, the container availability date; for exports, the earliest return date; the specific date(s) for which charges were assessed
Rates	Total amount due; the applicable rule (tariff and rule number, terminal schedule, or service contract number and section); the specific rate(s)
Disputes	An email, phone number or other contact for questions and mitigation, refund or waiver requests; a URL, QR code or similar link to a public page explaining what information to submit; the time frames for requests and responses
Certifications	A statement that the charges comply with the FMC's demurrage and detention rules, including the reasonableness rule at 46 CFR 545.5, and that the billing party's own performance did not cause or contribute to the charges

The deadlines

Step	Deadline	If it is missed
Billing party issues the invoice	Within 30 calendar days of the date the charge was last incurred	Billed party is not required to pay
NVOCC passes through a carrier's invoice	Within 30 calendar days of the date of the invoice it received	Billed party is not required to pay
Billed party requests mitigation, refund or waiver	Billing party must allow at least 30 calendar days from the invoice date	You may lose the right to dispute with the billing party
Billing party resolves the request	Within 30 calendar days of receiving it, or a later date both sides agree to	Grounds for an FMC charge complaint

When an NVOCC's customer disputes a charge, the NVOCC gets an additional 30 days to dispute with its own billing party.

How to dispute a charge

Check the invoice against the list above. A missing container availability date, free-time dates or certification is not a technicality; under the rule it means you do not owe the charge.
Check the dates. Was the invoice issued more than 30 days after the last day charged? Was the container actually available, with no customs or carrier holds and with appointments open, on the date the invoice says?
Gather evidence. Terminal availability screenshots, appointment system records showing no slots, gate tickets and equipment interchange receipts, emails about holds, and the empty-return location notices.
Request mitigation, refund or waiver in writing through the contact on the invoice, within the time frame it states (at least 30 days). Cite the specific dates and missing elements.
If the billing party does not resolve it, file a charge complaint with the FMC by email to chargecomplaints@fmc.gov. Include the bill of lading numbers and the invoices. There is currently no fee. Under the FMC's rule effective September 1, 2026, charge complaints may also be pursued through the Commission's formal or small-claims complaint procedures, which carry filing fees of $387 and $176.

The charge complaint process applies to charges assessed after June 16, 2022. If the FMC finds a violation it can order the charge refunded or waived, and civil penalties can follow in a separate proceeding.

Common mistakes

Paying first and reading later. Once paid, getting money back is harder than refusing to pay a defective invoice.
Missing the dispute window. Note the response deadline the day the invoice arrives.
No proof of unavailability. "There were no appointments" wins only with screenshots or system records from the day.
Confusing ocean detention with truck detention. They are billed by different parties under different rules.
Assuming truckers cannot be billed. That protection was removed in 2025. Read your interchange agreement and the carrier's terms before you accept a box.
Not passing the problem upstream. If a terminal closure or carrier hold caused the delay, the certification on the invoice says the billing party did not cause the charge. Challenge it.

Questions

What is the difference between demurrage and detention?

In general usage demurrage is charged for a container or cargo that stays in the marine terminal past free time, and detention or per diem is charged for a container kept outside the terminal past free time. Carriers do not all use the terms the same way, so read the tariff or contract. The FMC rule covers both, including per diem.

How long does a carrier have to send a demurrage or detention invoice?

Under 46 CFR 541.7 the billing party must issue the invoice within 30 calendar days of the date the charge was last incurred. If it misses that deadline, the billed party does not have to pay.

How long do I have to dispute a demurrage or detention invoice?

The billing party must give you at least 30 calendar days from the invoice date to request mitigation, a refund or a waiver. It then has to try to resolve your request within 30 calendar days of receiving it, unless you both agree to a later date.

Can an ocean carrier bill a trucking company for detention?

The FMC's rule originally limited billing to the consignee or shipper, which kept truckers off these invoices. A federal appeals court set that provision aside in September 2025 and the FMC removed it in December 2025. Whether a trucker can be billed now depends on the contracts involved, such as the interchange agreement. The invoice content and timing rules still apply.

Does it cost anything to file a charge complaint with the FMC?

There is currently no fee for the FMC's interim charge complaint procedure, which is submitted by email to chargecomplaints@fmc.gov. Formal complaints filed under the Commission's procedural rules carry filing fees.

Demurrage and Detention: The FMC Billing Rules and How to Dispute a Charge