Detention vs. demurrage, explained with real examples

The two words get used interchangeably on emails and invoices, and that is how money gets lost: a shipper disputes the wrong charge, a trucker eats a bill that was never theirs, or a warehouse gets blamed for days the box spent at the terminal. This guide separates the two clocks, shows what one carrier actually charges, and walks through the US billing rules that decide whether an invoice must be paid.

What is the difference between detention and demurrage?

The short version: demurrage is about where the box is (still inside the terminal), detention is about how long you have the carrier's equipment (outside the terminal). Terminology varies by carrier, so always read the tariff that applies to your bill of lading.

On exports the clocks run the other way: detention typically covers the time from picking up the empty to bringing it back loaded, and demurrage the time the loaded box waits at the terminal for its vessel. Check the tariff, because free time and the earliest date the terminal will accept the box both affect what you pay. The FMC treats per diem as part of detention and demurrage when it judges whether charges are reasonable (46 CFR 545.5).

How much do detention and demurrage cost per day?

It depends on the carrier, the port, your contract and how many days over you are. Rates usually step up in tiers the longer the box stays out. For a real reference point, here is one carrier's published US import tariff for dry 20ft and 40ft containers, effective 1 January 2026 and checked in October 2026:

Sources: Maersk US import detention tariff and Maersk US import demurrage tariff. In that tariff, a working day is a day the gate is open for pickup, Monday to Saturday. Other carriers and negotiated service contracts will differ, and the carrier's public tariff overrides any summary, including this one.

What about chassis charges?

A chassis is a separate piece of equipment with its own daily meter. In much of the US, chassis come from pools or leasing companies rather than the ocean carrier, and the trucker typically pays the pool and passes the charge on to the shipper. As a Rapid Ai 10x planning range, budget $30–$60 per chassis per day; check the pool or trucker's actual rate. When a container sits at a warehouse waiting to be unloaded, the chassis under it is usually on the clock too.

What does the FMC billing rule require?

The Ocean Shipping Reform Act of 2022 (OSRA 2022), signed on 16 June 2022, set minimum contents for detention and demurrage invoices and directed the FMC to write rules on them (FMC: OSRA 2022 implementation). The FMC's final rule, 46 CFR Part 541, Demurrage and Detention Billing Requirements, was published on 26 February 2024 and took effect on 28 May 2024, including the invoice-content section, §541.6 (89 FR 41895). As of October 2026, these are the main requirements:

Who it covers

Detention and demurrage invoices issued by ocean common carriers, marine terminal operators and NVOCCs (§541.2).

The 30-day deadlines

• Issue within 30 days. The billing party must issue the invoice within 30 calendar days of the date the charge was last incurred. If it does not, the billed party is not required to pay (§541.7(a)).
• NVOCC pass-through. An NVOCC billing a charge it received from a carrier or terminal must issue its own invoice within 30 calendar days of receiving the original (§541.7(b)).
• At least 30 days to dispute. The billed party must get at least 30 calendar days from the invoice date to request mitigation, a refund or a waiver (§541.8(a)).
• 30 days to resolve. The billing party must try to resolve the request within 30 calendar days of receiving it, unless both sides agree to longer (§541.8(b)).

What every invoice must show (§541.6)

• Bill of lading number, container number, and for imports the port of discharge.
• The basis for why the billed party is liable.
• Invoice date and due date.
• Allowed free time in days, and the free-time start and end dates.
• The container availability date (imports) or earliest return date (exports).
• The specific days charged, the rate or rates, the total due, and the tariff, terminal schedule or service contract that applies.
• A contact for questions and a link or code to a page that explains the dispute process and documents needed.
• A statement that the charges comply with FMC rules and that the billing party's own performance did not cause or contribute to them.

An invoice that leaves out required information removes the billed party's obligation to pay that charge (§541.5). Full text: 46 CFR Part 541 on eCFR.

What changed since 2024

The 2024 rule also limited who could be billed (§541.4). On 23 September 2025 the US Court of Appeals for the D.C. Circuit set that section aside in World Shipping Council v. FMC, and the FMC formally removed it effective 29 December 2025. The rest of the rule remains in effect (FMC final rule removing §541.4). Invoices must still explain why the billed party is liable.

Separately, the FMC judges whether detention and demurrage practices are reasonable by whether they work as incentives to keep freight moving (46 CFR 545.5). In 2026 the D.C. Circuit upheld an FMC decision that detention charged to a trucker who could not return equipment during a holiday port closure was unreasonable (FMC announcement, July 2026). The rule does not stop carriers charging; it requires the charge to be able to change someone's behavior.

How do detention and demurrage add up on a real shipment?

The numbers below are illustrative, rounded for easy math, and not any carrier's tariff.

How do you dispute a detention or demurrage charge?

1. Check the invoice against §541.6. Missing container number, free-time dates, the specific days charged, the rate source or the compliance statement are grounds to refuse payment of that charge.
2. Check the date. If the invoice was issued more than 30 calendar days after the charge was last incurred, you are not required to pay it.
3. Rebuild the timeline. Availability date, holds and releases, appointment requests and confirmations, gate-out and gate-in times, depot refusals or closures. Terminal and depot screenshots are evidence.
4. Request mitigation, refund or waiver in writing within the window stated on the invoice (at least 30 days), using the contact and process the invoice must name. Ask specifically about days when you could not pick up or return because of terminal closures, no available appointments, or a depot that would not accept the empty.
5. Escalate to the FMC if needed. Under OSRA 2022, anyone billed for a charge can file a charge complaint with the FMC. For detention and demurrage, the carrier has the burden of showing its charges are reasonable, and the FMC can order refunds (FMC charge complaint guidance).

How can a warehouse help shippers avoid detention and demurrage?

Demurrage is mostly decided before the box reaches you. Detention and chassis days are mostly decided at your dock. That makes the warehouse a real lever, and a selling point worth stating in every quote.

• Give delivery appointments quickly, ideally the same day the shipper or trucker asks, so pickup can be booked inside free time.
• Ask for the last free day and the container availability date with every inbound, and sort the dock schedule by it.
• Commit to a devan turn time you can actually hit (for example, same day or within 24 hours of arrival) and put it in the quote.
• Staff for the arrival pattern, including after-hours devans when the shipper agrees to the surcharge.
• Tell the trucker the moment the box is empty, and check the carrier's empty-return instructions so it goes to the right depot.
• Drop-and-hook where possible, so the chassis and the truck are not waiting with the box.
• Record arrival, devan start, devan finish and empty-ready times. These timestamps are the shipper's evidence in a dispute.

For what the unload itself costs and how waiting time stacks up against it, see how much it costs to unload a container. If your warehouse passes any of these charges through to customers, list them on your rate card as described in warehouse accessorial charges, and audit them with this pre-invoice audit.

Speed is what saves shippers detention, and speed starts with the quote. Adriana, the Rapid Ai 10x quoting agent, reads the inbound email, picks up the last free day and container details, and prices the devan and any accessorials from your rate card, with a person approving every quote. Luis turns the accepted quote into a scheduled job, and Chloe flags any after-hours or pass-through charges missing before the invoice goes out. See how the agents work.