A container stuck at the port is not just a growing bill; it is a bill you may be able to challenge. Demurrage applies while a full container sits inside the marine terminal, and detention applies while the carrier’s container is outside the terminal, from gate-out until the empty is returned. The models and generic guides explain those definitions and stop there. What they rarely mention is that in the US, the Federal Maritime Commission now regulates how these charges can be invoiced, who can be billed, and how fast you can dispute them, and that an invoice missing required information eliminates your obligation to pay until it is fixed. That changes what an importer should do when the first demurrage notice arrives.
When the clock actually starts
Demurrage begins when a container exceeds its free time on the terminal after discharge. The clock does not start when the vessel docks; it starts when the container is available for pickup, and the free days, the rate steps, and whether weekends count all come from the carrier’s tariff and the terminal’s rules. Detention works differently. It begins when the full container leaves the terminal, usually on the importer’s trucker, and runs until the empty is returned to the carrier’s designated depot. Carriers sometimes bill a combined demurrage and detention period, and the specific start times vary by carrier and port.
Because the clock is in the tariff, not in a sticker on the container, the first practical step when a container is stuck is to pull the tariff terms for that specific carrier and terminal; the billing party is required to apply them consistently, and the tariffs are generally published. If the terminal was closed for a holiday included in the counting rules, or the container was not actually available for pickup because the terminal had it on hold, those facts change the arithmetic and belong in your file.
Who can legally be billed
Under the Federal Maritime Commission’s final rule on detention and demurrage billing practices, effective May 28, 2024, an invoice can only be issued to one of two parties: the person for whose account the ocean transportation or storage was provided and who contracted for it, or the consignee, defined as the ultimate recipient of the cargo, the person to whom final delivery is to be made. An invoice cannot be issued to multiple parties at the same time.
This matters in the real world because bills get sent to whoever is easiest to reach: the broker, the trucker, the seller’s agent. If your facility is not the consignee and did not contract for the carriage, a bill addressed to you may fall outside the rule. The same logic protects small importers who are handed charges that actually belong to a party up the chain.
The invoice itself has teeth
The rule requires specific identifiable information to appear on each invoice. Here is the part most importers never hear: if any required information is missing, the billed party’s obligation to pay that charge is eliminated. This is not a technicality to exploit; it is a reason to inspect every demurrage and detention invoice line by line before paying, because the information requirements exist precisely so the charge can be verified against the movement it claims to bill.
Two more timing rules matter. Vessel-operating common carriers and marine terminal operators must issue these invoices within 30 calendar days from when the charges were last incurred, and non-vessel-operating common carriers must issue within 30 calendar days of the date of the invoice they received. Once you are billed, you have at least 30 calendar days to request fee mitigation, refund, or waiver, and if you file a timely request, the billing party must attempt to resolve it within 30 days unless both sides agree to more time. The FMC’s demurrage and detention page collects the rule, the data, and the complaint channels in one place.
Reading the free-time terms like a contract
Free time is not a courtesy; it is a number written into the carrier’s tariff, and it can be read before you book. When you pull the terms for a lane, look for four things. What counts as day one: discharge date, container availability, or the date the terminal posts the container as ready for pickup. What the free days apply to: calendar days or working days, and whether holidays in the terminal’s calendar are excluded. What the rate does after free time: whether it steps once or compounds, and whether the carrier bills per container or per day in aggregate. And what resets the clock: gate-out for demurrage, empty return for detention, and whether a re-stuff or inspection in between pauses the count.
Those four details decide almost every dispute. An importer who knows that free time runs in calendar days but the terminal was closed for two of them has a factual argument. An importer who assumed the same terms applied at both ports has nothing to argue with.
What to do when the zeros start accumulating
The instinct is to call everyone and argue. The file comes first. Collect the discharge date and container availability date from the terminal, the gate-out and empty return records if detention is involved, the free-time terms from the carrier’s tariff, and the invoice itself with its date. Compare each element against the rule’s requirements before deciding whether to pay, dispute, or request mitigation.
A well-built mitigation request is short and factual. State the container and invoice numbers, then walk through the timeline: when the container was discharged, when it was actually available, when your trucker attempted pickup, what blocked the release, and what you did to resolve it. Attach the terminal records, the appointment confirmations, and any correspondence showing the cause. The billing party must attempt to resolve a timely request within 30 days, so the request should be complete on first submission; a two-line complaint that the charge is unfair gives them nothing to approve.
Then move the cargo. Every dispute runs in parallel with real costs: chassis, storage, trucking that shows up and leaves empty. If the blockage is customs-related, the fastest fix may be correcting entry paperwork; our overview of China shipping delays covers the usual causes on the origin side, and for destination-side paperwork see the customs clearance page. If the blockage is trucking or appointment related, that is a scheduling problem, not a legal one: get a pickup slot committed in writing before the free time expires, not after.
Detention is a different animal
Detention is where most importers misread the bill. Demurrage is about the terminal wanting space back. Detention is about the carrier wanting its container back, and the clock starts when the full container leaves the gate, not when the vessel arrives. That means the count often starts while you are still unloading, and it keeps running through weekends, through your own warehouse delays, and through any repair the container might need before the empty is accepted at the depot. A container that sits empty in your yard for a week after unloading can generate more detention than the demurrage it avoided.
The practical control is scheduling the empty return before the container arrives. Confirm the depot’s hours, whether it accepts returns without an appointment, and what condition it will reject a container in. A chassis held because the depot is closed on Saturday is still billed against you, and arguing about it afterwards rarely recovers the charge.
The origin side gets demurrage too
Importers focus on the destination port, but the same mechanics run at the load port in China. If a supplier’s factory cannot deliver the container before the terminal cutoff, or the export customs release comes late, the container can miss its vessel and either roll to the next sailing or sit at the origin terminal accruing charges. Who bears that cost depends on your Incoterms and on what your contract with the supplier says about cargo-ready dates and cutoff obligations.
Practical prevention at origin looks different from destination. Instead of booking pickup trucks, you police a schedule: cargo-ready date confirmed in writing, the factory’s delivery to the terminal booked with buffer before the cutoff, and export documentation prepared in advance. When a supplier pushes delivery to the last day before cutoff, the shipment is one customs query away from origin demurrage, and that cost usually lands on whoever the contract says is responsible for the missed vessel. Asking for the cargo-ready confirmation two weeks before the cutoff is cheaper than discovering it slipped after the booking closed.
Prevention beats dispute
Free time is negotiable at the contract level. Large shippers negotiate free days into their service contracts; smaller importers usually inherit whatever the tariff offers. Two habits shrink the exposure regardless of size. First, plan pickup before the vessel arrives: know the arrival date, book the trucker and the delivery appointment in advance, and confirm the terminal will release the container once the entry clears. Second, treat the destination side of your own operation as part of the shipment. The single most common source of demurrage is that the importer was not ready when the container was.
For recurring lanes, ask what the carrier’s free-time terms actually are, in days, per container type, and confirm what triggers the first paid day. A forwarder who moves your cargo regularly can usually tell you which terminals in a given port have the tightest windows, which is knowledge worth having before the invoice, not after.
FAQ
Does signing the delivery receipt waive my demurrage dispute?
No. The billing dispute regime is separate from accepting delivery of the cargo. Signing for the cargo and receiving the container does not by itself waive your right to request mitigation, refund, or waiver of a charge that was billed contrary to the rules.
Can the forwarder just pay the terminal and bill me later?
That is common practice, and it can bury the issue. If a forwarder pays to release the container and passes the charge to you later, ask for the original invoice and the movement records. The rule’s information requirements apply to the invoice in the chain, and your ability to dispute depends on seeing the actual document before deadlines pass.
My container sat on the terminal because customs held it. Who pays?
Usually the importer, which is why the fastest fix for a customs hold is a corrected filing. That said, if the hold was caused by a party required to have their paperwork in order and the facts show it, that supports a mitigation request. The 30-day window is for exactly this kind of submission, made with records rather than arguments.
Is this rule only about US ports?
The FMC’s billing rule governs US trades under the Shipping Act. Other markets have their own regimes and their own free-time norms. If you import into the EU, UK, or elsewhere, assume the local carrier and terminal tariffs control and check them directly; the discipline of verifying invoices against movement records travels everywhere.
The takeaway
Demurrage and detention are the only two shipping charges where the US regulator has explicitly said a defective invoice removes the obligation to pay. Importers who know that check their invoices instead of absorbing them, and who know the billing windows act inside the deadlines instead of after them. Neither habit costs anything, and both are worth more than the average negotiation over a few free days.
