Demurrage, detention and per diem explained: a Canadian shipper’s guide

Demurrage, detention, per diem and storage are all charges for keeping a container, or terminal space, longer than the free time allows. They come from different parties and start at different moments, and in Canada rail storage adds one more clock. This guide explains each one and how to keep them under control.

Last updated: 24 October 2026

The short version

Charge	What it is for	Usually billed by
Demurrage	The shipping line’s container sitting inside the terminal, port or depot past free time	The shipping line
Detention	The shipping line’s container kept outside the terminal past free time, until the empty is returned	The shipping line
Per diem	A daily equipment-use charge once free time ends. In North America it often means detention under the UIIA	The equipment provider, invoiced to the motor carrier
Storage	Using terminal or rail-yard space past free time	The terminal operator or the railway

Exact definitions differ between companies. Always read the tariff or contract that applies to your shipment.

Demurrage

Maersk’s published terms are a good example of how shipping lines define it. Demurrage is “compensation payable when the Merchant holds Carrier’s Container inside the terminal, port or depot beyond the agreed amount of Free Time.” For an import, the demurrage clock starts when the container is discharged from the vessel and stops when it gates out of the port.

Demurrage usually builds up when a container can’t leave the terminal: customs holds, unpaid freight, a missing release, or no truck booked.

Detention

Detention is the other half. In Maersk’s terms it is payable when the merchant “holds Carrier’s Container outside the port, terminal or depot beyond the agreed amount of Free Time.” For an import, it runs from gate-out until the empty container is returned to the agreed terminal, port or depot.

Detention builds up when your dock can’t unload quickly, when a drop container sits in a yard, or when the empty can’t be returned (for example, when the return location isn’t accepting empties).

Combined demurrage and detention

Some lines give a single combined free-time allowance that covers time both inside and outside the terminal. Whether a line charges demurrage and detention separately or combined depends on the line and the country, so check the line’s local tariff page.

Per diem

“Per diem” literally means “per day”. In North American intermodal trucking it usually refers to the daily charge for keeping an equipment provider’s container or chassis past free time. Most of these interchanges run under the UIIA (Uniform Intermodal Interchange and Facilities Access Agreement). The Intermodal Association of North America describes it as the standard industry contract between intermodal motor carriers and equipment providers, used for about 95% of North American intermodal equipment interchanges. Under the UIIA, free time and rates are set by each equipment provider, not by the agreement itself.

This matters in Canada too. Montreal Gateway Terminals, for example, says carriers collecting import or empty containers there for several shipping lines must subscribe to the UIIA. A per diem invoice typically goes to the drayage carrier, which passes it on to whoever hired it, so agree on that in advance.

Rail storage in Canada: the extra clock

When an import container moves inland by rail, the railway’s storage rules apply at the destination terminal, separate from the shipping line’s demurrage and detention.

CN

Storage charges are set in CN’s optional services tariff, CN 9100.
Storage guarantees must be made through CN’s eBusiness tool, Intermodal Shipment Status. CN no longer accepts faxed or emailed guarantees.
The tool shows the first day of storage and any amount owing, and the balance must be $0 before pick-up can be arranged.
At Brampton, CN says containers arriving without a gate appointment could be shuttled to its Mississauga terminal, with a $150.00 storage fee.

CPKC

CPKC’s intermodal tariff, CPKC 3 (effective 1 November 2025), separates two charges:

Detention for extended use of CPKC-supplied equipment
Storage for non-CPKC equipment, such as steamship-line containers, held at CPKC terminals

For steamship-line containers in import and export service, the tariff gives 24 hours of free time at Vaughan and Lachine and 48 hours at the other terminals it lists. The clock starts at 00:01 after the unit is available for pick-up. Weekends and legal holidays count when the terminal is open, and charges are per day, per unit. The tariff makes the payer of freight responsible. Units that dwell past free time can be moved to an offsite location, for a listed fee of $500 per unit on top of storage, and no extra free time is given.

Railway tariffs change. Check the current version before you rely on any figure.

How one late import can collect several charges

Picture a container that arrives at an inland rail terminal while its customs release is delayed. Railway storage can start once the railway’s free time runs out. Depending on the line’s terms, the line’s demurrage or combined free time may also be running. After pick-up, if the importer’s dock is full and the container waits several days, detention builds. If a drayage carrier pre-pulled it to its yard, yard storage and chassis days may be added. Each charge comes from a different party, so they are easy to miss until the invoices arrive.

How to avoid demurrage, detention and storage

Know your free time per party: shipping line (demurrage, detention or combined), railway (storage) and drayage carrier (waiting time, yard storage, chassis).
File customs entries early so the release is ready when the container is available.
Book drayage before arrival, especially at terminals with short free time.
Use pre-pulls when your dock can’t take the container in time. Paying a carrier for yard storage can cost less than terminal storage or demurrage. Compare before deciding.
Plan the empty return and confirm the return location with the line.
Negotiate extra free time with the shipping line on your contract if your operation needs it.
Check every invoice against the dates: discharge, availability, gate-out, delivery and empty return. Dispute errors quickly. Under the UIIA, disputes over per diem can go to its binding arbitration process.

FAQ

What is the difference between demurrage and detention?

Demurrage covers the line’s container inside the terminal past free time. Detention covers it outside the terminal until the empty is returned.

Is per diem the same as detention?

Often, in North American practice. Per diem is a daily equipment-use charge after free time, usually billed to the motor carrier under the UIIA.

Who pays rail storage in Canada?

CPKC’s tariff makes the payer of freight responsible. At CN, the balance must be cleared through its eBusiness tool before pick-up. Who pays in the end depends on your contracts.

How much free time do I get?

It depends on the shipping line, your contract, the terminal and the railway. Check your arrival notice, the line’s tariff and the railway’s tariff.

Find a carrier who can move your container on time

The quickest way to avoid storage is a carrier that already has access to your terminal. Find carriers by terminal: CN Brampton, CPKC Vaughan, Port of Vancouver or Port of Montreal. To request a quote, open a carrier’s page and contact that company directly.

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