Demurrage vs Detention: Clocks, Costs & Prevention

Demurrage is usually charged when a container stays inside a terminal or depot beyond free time; detention is usually charged when carrier equipment remains outside beyond free time. Storage may be a separate terminal charge. Exact clocks, rates, exclusions, and billing parties depend on the tariff, contract, port, carrier, and jurisdiction.

Both charges are easier to prevent when the buyer manages milestones rather than memorizing definitions. Arrival notice, customs release, terminal availability, pickup appointment, unloading, and empty return can each consume a different clock. A cheap ocean rate can become expensive when nobody owns those dates.

Demurrage vs detention in one table

Question	Demurrage	Detention	Storage
Where is the container?	Usually inside the terminal or depot.	Usually outside the terminal or depot in the merchant's or haulier's use.	Occupying terminal, port, warehouse, or yard space.
What is being charged?	Container time beyond allotted terminal free time.	Use of carrier equipment beyond allotted outside free time.	Use of physical storage space.
Who commonly bills it?	Shipping line or carrier, subject to local practice.	Shipping line or carrier.	Terminal or port, sometimes passed through by a carrier.
Typical stop event	Container leaves the terminal, subject to the governing rule.	Empty container is returned to the accepted location, subject to the governing rule.	Goods or equipment stop occupying the billed space.
Can it overlap another charge?	It may overlap storage in some billing structures.	It may follow demurrage as the container moves outside.	It may be assessed at the same time as demurrage.

The Digital Container Shipping Association glossary uses the inside-versus-outside distinction and warns that storage can be separate from demurrage. The U.S. Federal Maritime Commission similarly describes detention as extended equipment use and demurrage as time beyond free time on a marine terminal. These standard descriptions are a starting point, not a substitute for the charge rule governing a specific shipment.

What container free time means

Free time is a period during which the relevant demurrage, detention, or storage charge does not accrue. It is not necessarily one combined allowance. A carrier can provide one period for terminal use and another for equipment use. A terminal may apply its own storage schedule. Weekends, holidays, port closures, customs holds, or appointment failures may or may not pause a clock.

Buyers should obtain the governing tariff, service-contract term, terminal schedule, and carrier confirmation rather than relying on a verbal “seven free days.” The useful questions are:

Which charge does the free-time promise cover?
What event starts the count: discharge, availability, notice, or another event?
Are calendar days, business days, weekends, and holidays treated differently?
What event stops each clock?
Does the rate increase in tiers?
Which party invoices the charge and which party can approve a waiver?
What evidence is required to challenge an invoice?

How the clocks start and stop

A simple import flow can contain several relevant events: vessel arrival, container discharge, cargo availability, customs release, terminal appointment, gate-out, delivery to the buyer, unloading, and empty return. The order matters. Customs release does not always mean the container is physically available, and cargo availability does not mean a pickup appointment exists.

Before arrival: the forwarder confirms estimated arrival, free-time terms, documents, customs filing, and terminal requirements.
After discharge: the buyer records the actual availability event used by the applicable charge rule.
Before gate-out: customs, carrier, terminal, payment, appointment, and trucking holds are cleared.
Outside the terminal: the receiver unloads promptly and protects the empty-return appointment.
At empty return: the haulier records the accepted return event, location, date, and equipment condition.

The broader cargo arrival process explains the operational sequence. A demurrage-and-detention review should add exact charge clocks to that sequence.

Why storage is not automatically demurrage

Demurrage and storage both relate to time inside a terminal, so people often use the words as if they were synonyms. Commercially, they can be separate. Demurrage generally relates to a carrier's container remaining in the terminal beyond free time. Storage generally relates to the space occupied at the terminal, port, warehouse, or yard.

A terminal can invoice storage while the carrier invoices demurrage, meaning both charges accrue for the same calendar period. In another port, the carrier may collect a combined or passed-through charge. An invoice review must identify the legal or contractual source of each line item instead of rejecting a charge merely because a second charge covers similar days.

An illustrative import timeline

Illustrative example: A full container is discharged and becomes available on a Monday. The applicable carrier and terminal documents—not a universal industry rule—give the importer a defined terminal free-time window. A documentation hold is cleared late, and the first available trucking appointment is after that window. The container then leaves the terminal.

For the first calculation, the buyer identifies the start event, the final free day, the gate-out timestamp, and any rule that excludes a day. Chargeable demurrage days are the days after the applicable free period and before the governing stop event. The buyer then checks whether a separate terminal storage schedule covers the same period.

After gate-out, a separate equipment-use period applies. The receiver unloads slowly and returns the empty container after the applicable detention-free period. Chargeable detention days are calculated under that separate rule. The buyer should not add the two clocks together and call the result “demurrage.”

No currency rate or universal number is used here because a carrier tariff can use escalating tiers, a negotiated service contract can provide different terms, and local law can affect invoice practices. The example teaches the calculation sequence: identify the charge, source, start event, free period, stop event, exclusions, and rate tier.

Who controls each milestone?

Milestone	Primary owner to assign	Evidence to retain
Arrival and availability monitoring	Forwarder or import operations lead	Carrier and terminal event notices
Original or electronic transport-document release	Buyer and seller payment/document teams	bill of lading release status and correspondence
Customs entry and release	Importer and customs broker	Entry submission, holds, queries, and release
Terminal payment and appointment	Forwarder or haulier	Receipts, portal status, and appointment confirmation
Pickup and delivery	Haulier and receiver	Gate ticket, delivery proof, and timestamps
Unloading and empty return	Receiver and haulier	Unloading record, return appointment, interchange receipt, and photos

The exact party paying an invoice depends on the transport and sales contracts. Even when a freight forwarder coordinates the move, the importer should know who is authorized to accept extensions, appointments, substitute return depots, and invoice disputes.

Prevention checklist before vessel arrival

Obtain the carrier tariff or negotiated free-time confirmation in writing.
Separate carrier demurrage, carrier detention, and terminal storage terms.
Confirm the shipment's FCL shipment planning assumptions; do not apply container-equipment logic blindly to LCL shipment planning.
Pre-clear commercial invoice, packing list, origin, permits, and transport documents.
Assign one person to monitor availability rather than relying only on an arrival email.
Reserve a haulier and receiving slot before the final free day.
Plan labour, dock space, and equipment for immediate unloading.
Confirm where the empty container must be returned and whether that depot accepts it.
Keep screenshots and timestamps if a carrier or terminal system blocks pickup or return.
Escalate before free time expires; a later complaint is weaker than a contemporaneous request.

How to review a charge invoice

Start with one line item at a time. Identify the billed equipment, container number, shipment, charge name, issuing party, tariff or contract, free-time grant, start event, stop event, billed dates, daily tiers, taxes, and prior payments. Then compare the invoice against source records.

A useful evidence file can include the booking confirmation, bill of lading, arrival and availability notices, customs release, terminal holds, appointment attempts, gate ticket, delivery proof, empty-return receipt, depot rejection, carrier correspondence, and screenshots with dates. If a waiver or dispute is justified, state the exact days and rule at issue instead of asking generally for “all demurrage” to be removed.

For complex movements, AeonixTrade's shipping coordination support can help buyers organize milestones and document handoffs. It cannot override the carrier, terminal, customs authority, governing contract, or applicable law.

Frequently asked questions

Does demurrage stop when the container leaves the terminal?

That is the usual operational distinction, but the invoice must be checked against the applicable tariff or contract. Gate-out evidence is therefore important.

When does detention start?

Detention generally relates to equipment time outside the terminal after the applicable free period. Its exact start event and counting method come from the governing terms.

Can storage and demurrage be charged together?

Yes, in some billing structures. Storage can be a terminal space charge while demurrage is a carrier container charge. Other structures may combine or pass through charges.

Who pays demurrage and detention?

The carrier or terminal invoice and the transport and sales contracts determine responsibility. Importers should not assume that an Incoterm alone answers every local charge allocation.

What is the fastest prevention step?

Assign ownership before arrival. Confirm free-time terms, pre-clear documents, book trucking and receiving capacity, and track the actual start and stop events in one shared timeline.

Demurrage vs Detention: Which Container Clock Is Costing You?