Demurrage vs detention: what each charge is and which invoices the rule covers
Demurrage accrues when a container stays on a marine terminal past its free time, and detention is charged for extended use of intermodal equipment. The FMC billing rule defines the two as one term and covers an invoice for either charge when an ocean common carrier, a marine terminal operator or an NVOCC issued it. An invoice from anyone else is outside the words of the rule.
Updated . Status as of
What each charge is
The Federal Maritime Commission puts it in one sentence: "Detention is charged for extended use of intermodal equipment and demurrage accrues when a container exceeds free time on a marine terminal." Free time is the number of days the invoice allows before the charge starts. The sentence is on the FMC page on detention and demurrage.
| Charge | What the source says | Source |
|---|---|---|
| Demurrage | It accrues when a container exceeds free time on a marine terminal. | FMC, detention and demurrage |
| Detention | It is charged for extended use of intermodal equipment. | FMC, detention and demurrage |
| Demurrage or detention, as one term | Any charges, including "per diem" charges, assessed by ocean common carriers, marine terminal operators, or non-vessel-operating common carriers related to the use of marine terminal space (e.g., land) or shipping containers, but not including freight charges. | 46 CFR 541.3 |
The rule does not set the two charges apart. It defines "demurrage or detention" as a single term, so a charge called per diem is inside the definition when it is related to the use of marine terminal space or shipping containers. Freight charges are not part of it. What decides whether the rule applies to an invoice is who issued it and what it charges for, not the name printed above the amount.
Which invoices the rule covers
| Question | What the rule and the FMC say | Source |
|---|---|---|
| Who issued the invoice? | The rule governs any invoice issued by an ocean common carrier, marine terminal operator, or non-vessel-operating common carrier for the collection of demurrage or detention charges. | 46 CFR 541.2(a) |
| What does it charge for? | Demurrage or detention. Freight charges are not part of that term. | 46 CFR 541.3 |
| Between whom? | The part does not govern the billing relationships among and between ocean common carriers and marine terminal operators. | 46 CFR 541.2(b) |
| From when? | The FMC says the rule went into effect on May 28, 2024. | FMC, court decision on the billing rule |
| Who may be billed? | Section 541.4 once said who a demurrage or detention invoice may be sent to. On September 23, 2025 a court set it aside; the FMC says the rest of the rule remains in effect. The eCFR now shows 541.4 as reserved. | FMC, court decision on the billing rule; eCFR, 46 CFR part 541 |
An invoice from a trucker, or from a freight forwarder that is not an NVOCC, is not issued by any of the three named kinds of company, so it is outside the words of section 541.2(a) (46 CFR 541.2). DemurrageCheck marks such an invoice, and an invoice dated before the rule took effect, as outside the rule instead of checking it.
What the rule asks of a covered invoice
Section 541.6 lists the minimum information a covered invoice must contain: the identifying information, the timing information, the rate information, the dispute information and two statements from the billing party (46 CFR 541.6). Section 541.5 says that failure to include any of it "eliminates any obligation of the billed party to pay the applicable charge" (46 CFR 541.5).
| Limit | What the rule says | Source |
|---|---|---|
| Issuing the invoice | Within 30 calendar days from the date on which the charge was last incurred. | 46 CFR 541.7(a) |
| An NVOCC passing a charge on | Within 30 calendar days from the issuance date of the invoice it received. | 46 CFR 541.7(b) |
| Asking for mitigation, refund, or waiver | The billing party must allow the billed party at least 30 calendar days from the invoice issuance date. | 46 CFR 541.8(a) |
| The answer to that request | The billing party must attempt to resolve it within 30 calendar days of receiving it, or at a later date agreed by both parties. | 46 CFR 541.8(b) |
The FMC adds that the provisions on accurate and sufficient information and on the 30-day issuance deadline stay fully applicable after the court decision, and that failure to comply with either of them eliminates any obligation of the billed party to pay the applicable charge (FMC, court decision on the billing rule).
What DemurrageCheck does with this
- It checks each invoice for the items of section 541.6 and for the issue and request-window limits (541.7(a), 541.7(b) and 541.8(a)), and shows the paragraph each finding rests on. The list is on the how it works page.
- It does not decide who should have been billed, because the court set aside section 541.4 (FMC). It checks that the invoice states a basis for billing the party, not whether the basis is right.
- It prepares a letter for you to send from your own company. It does not contact the carrier, and the carrier decides what to answer.
Sources
- 46 CFR part 541 (eCFR): The scope, the definitions, the required contents of an invoice and the time limits (sections 541.2, 541.3, 541.5, 541.6, 541.7, 541.8)
- FMC, detention and demurrage: The FMC description of detention and of demurrage
- FMC, U.S. Court of Appeals issues decision in case on demurrage and detention billing practices: The effective date of the rule, section 541.4 set aside, and the rest of the rule in effect
This guide is general information about a federal rule, not legal advice. DemurrageCheck is software, not a law firm. Read the rule itself for its exact wording.
Next step
Upload the invoices you have and see which items of the rule each one lacks. The free check covers 10 invoices.