Demurrage vs Detention: What Each Covers and How to Check

Many freight teams approve a demurrage or detention line the way they approve any accessorial: the container number matches a shipment, the day count looks plausible, the rate is printed on the invoice. That works when one carrier bills one clean period on a container that moved on time. It misses the cases where the two charges start from different events, overlap, or arrive after the container is back in the depot.

What is demurrage, and what is detention in shipping?

Demurrage is usually the charge a carrier applies when its container stays inside the terminal, port or depot beyond the free time allowed, most often while still loaded. Detention usually applies when the container stays outside the terminal, in the shipper's or consignee's hands, beyond the free time allowed and until the empty is returned. Together the two are often written as D&D.

The precise wording is each carrier's. Maersk's terms for detention and demurrage define demurrage as compensation for holding the container "inside the terminal, port or depot beyond the agreed amount of Free Time", detention as the same "outside the port, terminal or depot", and a third case, combined demurrage and detention, for "the combined period of inside and outside the terminal".

Usage is not uniform. Some carriers and markets use "detention" for the whole period, others bill the equipment charge as per diem, a term the FMC's US rule folds into its definition of demurrage and detention. German-language invoices often carry the lines as Liegegeld or Standgeld, and which word covers which period follows the carrier's glossary. The tariff or contract in force decides what the line means.

The typical demurrage vs detention differences, with the caveat that a specific tariff can define any cell differently:

How are demurrage and detention charges counted against free time?

Free time is the period the carrier allows before a demurrage or detention charge starts, as set out in the tariff or negotiated contract.

The invoice may not show all three, so the reviewer often has to rebuild the count from the invoice, the tariff and the shipment records.

Maersk's terms, for instance, run import free time from discharge to gate-in of the returned empty when the allowance is combined, and split it at the terminal gate when the two are separate. Whether the days are calendar days or exclude weekends and port holidays is a tariff rule that differs by country and carrier; Maersk's FAQ on demurrage calculation says its charges are "calculated according to local country guidelines". A combined free time allowance behaves differently again: a slow pick-up uses up days that would otherwise cover the return leg.

Dwell is where the count begins. In the invoices audited on our platform in the first nine months of 2026, demurrage, detention and storage lines billed above the contracted rate or with no contracted rate at all came to about CHF 215,000 across at least three clients, with demurrage alone close to half. Each additional chargeable day adds to the bill.

In the US, the count is also regulated for the billing parties the FMC oversees. The Federal Maritime Commission's final rule on demurrage and detention billing, published 23 February 2024 and in full effect from 28 May 2024, applies to the ocean carriers, NVOCCs and marine terminal operators the FMC regulates. The rule also limited who could be billed to the party that contracted for the transport or storage, or the consignee, but the US Court of Appeals for the D.C. Circuit set that provision aside on 23 September 2025. That specific restriction no longer applies, so who can be billed depends on the applicable contract and other governing requirements. The FMC confirms the rest of the rule remains in effect. Vessel-operating carriers and marine terminal operators must issue the invoice within 30 calendar days of the day the charge was last incurred; an NVOCC has 30 days from receiving the underlying invoice. The billed party gets at least 30 calendar days to request mitigation, refund or waiver. Under 46 CFR 541.6 the invoice must show, among other items, the bill of lading and container numbers, the free time allowed and its start and end dates, the availability date for imports or earliest return date for exports, the dates charged, the rate and the tariff or contract rule behind it, and dispute contact details. The FMC states that a missing required item "eliminates any obligation of the billed party to pay the applicable charge".

Why do these lines get approved without a check?

Because each input that decides the amount sits with a different party: the carrier holds the tariff, the terminal the dates, the haulier the return receipt, and the approver only the result. Five patterns recur:

• Different triggers. Demurrage counted from discharge and detention from the day the box left the terminal give one container two start dates; applying one date to both is wrong on one of them.
• Weekends and holidays. A tariff that excludes them and an invoice that counts them differ by two days a week and more around public holidays, and the invoice does not say which it did.
• Combined versus separate allowances. Under a combined allowance the return leg is charged from the day the total runs out; under separate allowances each leg has its own free period.
• Late invoices. A line that arrives weeks after the container return is approved from memory. Where the FMC's rule covers the invoice, its 30-day deadline applies; elsewhere the contract sets the limit, if any.
• Pass-through billing. A forwarder or other intermediary may re-bill the carrier's charge under its own contractual terms, so the line is checked against the agreement behind that invoice as well as the underlying carrier charge.

How do you check a demurrage or detention line?

Treat the line as evidence of a count, not proof of one, and rebuild the count:

Our Invoice Approval module puts this check in front of the payment run: each line is matched against the shipment and the rate card, and exceptions that do not fit the contracted terms, including charges with no contracted rate, go to a reviewer to approve or reject before payment. A demurrage or detention line that cannot be tied to a free time rule can then be rejected and reissued rather than paid and claimed back months later.

Free freight audit, 100 shipments

We audit 100 of your shipments and show you the savings.

• Send the invoices and the contract or tariff for 100 recent shipments, including any demurrage and detention lines.
• We check each line against the contracted rates and free time, using the shipment dates.
• You get a written summary of the lines with grounds for a claim and the terms that produced them.

You'll meet Alexandre de Perregaux
CEO & Founder, Intellyse

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