Demurrage vs detention vs per diem: who bills what.

Demurrage, per diem, and trucker detention: the core differences

In container drayage, accessorial fee misunderstandings directly erode operating margins. Moving intermodal freight through marine container terminals and inland rail ramps requires operational clarity. A single container delay can trigger multiple invoices from different commercial entities, each using conflicting terms for what seems like the same delay.

Dispatchers and motor carrier owners must separate three distinct charges:

• Demurrage is the storage fee assessed when a loaded container remains inside a marine terminal or rail ramp past allotted free time. Yard space on docks and rail ramps is limited. Once a container is grounded, free storage days count down. If the container is not out-gated before that window closes, the facility charges demurrage for each additional calendar day. Free time allowances and daily storage tiers vary by facility, so operators should check the current terminal or rail ramp tariff for specific rates.

• Per diem is the equipment usage fee assessed by an ocean shipping line for retaining their container outside the terminal past permitted equipment free days. Ocean carriers own or lease the physical box. When a trucker pulls a container, the line expects it returned to an authorized yard within an agreed window. If it stays on the street longer, the line bills per diem daily until return. Equipment free time and daily rates vary by ocean carrier, so carriers should check the current ocean line equipment tariff.

• Trucker detention, often called driver waiting time, is an accessorial fee billed by the motor carrier to its paying customer. This fee compensates the carrier when a driver and tractor are delayed at a customer warehouse or terminal gate beyond an agreed free waiting window. Unlike demurrage and per diem, trucker detention covers wasted driver labor and tied-up equipment capacity. Contractual free time and hourly rates vary by contract, so carriers should confirm terms in their customer rate agreements.

Clear operational definitions protect your business from absorbing costs that belong to other parties in the supply chain.

Who bills whom across ocean carriers, terminals, chassis pools, and truckers

Container supply chains rely on interlocking commercial agreements. Responsibility for a fee depends heavily on whether the movement is booked under merchant haulage, where the cargo owner or forwarder hires the trucker, or carrier haulage, where the ocean line arranges inland delivery.

In merchant haulage, financial pathways branch across four distinct entities:

• Marine terminals and rail ramps bill demurrage to either the cargo owner or the motor carrier before releasing the container. If demurrage is owing, the facility locks release until payment is settled. Because payment rules and release procedures differ across facilities, carriers should check current payment terms in the governing terminal or rail tariff.

• Ocean shipping lines bill per diem directly to the motor carrier that pulled the container under an equipment interchange contract. Even if an inland delay was caused by a slow receiver, the ocean line looks to the trucker for payment. Because allowed days and daily rates vary across lines, carriers should check the specific line equipment tariff.

• Chassis leasing providers bill daily usage fees directly to the motor carrier under commercial pool agreements for every day a chassis remains checked out under a container.

• Drayage motor carriers bill customers for linehaul and legitimate accessorials, including driver waiting time, chassis usage and split fees, and pass-through demurrage or per diem paid on the customer behalf.

Because lines and chassis pools bill the trucker first, dispatchers must document every delay immediately to re-bill charges successfully.

Ocean line detention versus trucker detention: clearing up the vocabulary trap

One of the most persistent points of friction in intermodal freight is the word detention. Ocean shipping lines and trucking companies use the exact same term to describe two completely different events.

In steamship line tariffs, equipment detention is simply another name for per diem. The shipping line views the container as detained away from the equipment pool. When an ocean carrier invoice lists detention, it refers to calendar days the container spent on the street past equipment free time.

In trucking operations, detention refers strictly to driver waiting time. When a driver arrives at a customer facility and waits for an open dock door, that delay is trucker detention, representing idle labor and tied-up tractor capacity.

This dual usage creates confusion on invoices: a customer may think they are billed twice for one delay, or a dispatcher may read an ocean bill for detention as a driver delay.

To eliminate confusion, label driver waiting time explicitly as driver waiting time or truck detention. Label equipment charges as ocean container per diem or equipment per diem.

When disputes escalate, regulators may have a say, and the rules differ by country and mode. In the United States, the Federal Maritime Commission oversees ocean carrier practices on demurrage and detention. In Canada, ask the Canadian Transportation Agency or your lawyer which rules cover your move. Rules and billing requirements change, so check the current ones before you rely on this summary.

Chassis fees are a separate bill

Chassis usage is a fourth charge. The pool bills the carrier a daily rate from the moment the chassis is picked up until it is scanned back in, and a split fee can apply when the chassis and the container are at different places. Pool billing errors are common, so reconcile each statement against your own records. Our guide to disputing chassis invoices shows how.

A complete container movement: worked timeline and fee calculation

To understand how demurrage, per diem, chassis fees, and trucker detention interact during an import delivery, consider the following practical scenario.

Note: The following timeline, dates, hourly rates, and daily fee amounts are an invented, made-up illustration using round numbers. All rates and fees are purely illustrative to demonstrate how multiple charges accumulate on a single import container.

Imagine an import forty-foot container arriving by ocean vessel at a marine terminal, with cargo destined for an inland warehouse under merchant haulage arranged by a freight broker.

Here is the operational timeline of the container movement:

• Day 1 (Monday): Vessel unloads container to the terminal stack. The ocean line allows 5 calendar days of equipment free time (Days 1 through 5). The terminal tariff grants 4 calendar days of free storage time (Days 1 through 4).
• Day 3 (Wednesday): Customs releases the box, and the terminal marks it physically available for pickup.
• Day 4 (Thursday): Final free storage day. The dispatcher attempts to book an appointment for Friday, but no reservation slots are available.
• Day 5 (Friday): The box remains stacked. This is the last free day for ocean per diem. The terminal charges its first day of demurrage.
• Day 6 (Saturday): The terminal is closed for weekend gate operations, accruing a second day of demurrage.
• Day 7 (Sunday): The terminal remains closed, accruing a third day of demurrage.
• Day 8 (Monday): The carrier secures an appointment slot. The driver bobtails to an off-dock chassis depot to mount a bare chassis, incurring a chassis split. At the terminal, the carrier settles 3 days of demurrage to release the box. The driver arrives at the receiver warehouse at 10:00. Free waiting time is 2 hours. Due to dock congestion, unloading finishes at 15:00, creating 3 hours of excess waiting time.
• Day 9 (Tuesday): The carrier attempts an empty return, but the ocean line directs empties to an off-dock yard that is full and turns the driver away.
• Day 10 (Wednesday): The ocean line redirects empties to an alternative depot. The driver drops the empty box at 11:00 and returns the chassis to the pool at 13:00.

Here is the financial breakdown of the accessorial charges accumulated on this single container:

• Terminal Demurrage: 3 days past free time (Days 5, 6, 7). At an illustrative rate of $200 per day, total terminal demurrage is $600.
• Chassis Split Accessorial: Flat accessorial fee billed to the customer for fetching a chassis from an off-dock pool. Illustrative flat fee of $120.
• Chassis Daily Usage: Bare chassis in use from Day 8 through Day 10 (3 days). At an illustrative pool rate of $35 per day, chassis usage cost is $105.
• Trucker Detention: 3 hours of waiting time past the 2 contractual free hours. At an illustrative rate of $80 per hour, billable driver detention is $240.
• Ocean Line Per Diem: 5 billable days past equipment free time (Days 6 through 10). At an illustrative rate of $150 per day, the ocean line bills $750.

Total accessorial and detention costs reach $1,815. The motor carrier bills the customer for legitimate accessorials: $240 driver detention, $120 chassis split, and $105 chassis usage.

Meanwhile, the carrier faces $600 in terminal demurrage and $750 in ocean per diem that accumulated due to unavailable terminal appointments, weekend closures, and empty return restrictions. Without detailed operational records, the carrier risks paying these charges out of pocket.

Building an unshakeable audit trail and dispute packet

Disputing invalid demurrage and per diem invoices requires hard evidence. Ocean shipping lines and terminal operators will not waive fees based on unverified verbal reports. Carriers must build a chronological, documented packet proving that delays resulted from events outside their control.

Every drayage carrier should maintain six essential records:

• Date-stamped appointment logs: Screenshots or system logs proving appointment attempts before the last free day showing that no booking slots were available.
• Equipment Interchange Receipts: In-gate and out-gate slips from marine terminals, rail ramps, and chassis depots recording container numbers, chassis numbers, dates, and exact timestamps.
• Terminal operational notices: Official bulletins documenting gate closures, system outages, crane breakdowns, severe weather suspensions, or holiday operating schedules.
• Ocean carrier equipment return bulletins: Archived equipment advisories or emails showing empty return restrictions, gate cutoffs, or diverted depot instructions.
• Automated geofenced GPS records: Telematics data recording the precise minute a truck enters and departs customer facilities, marine terminals, and chassis depots.
• Signed proof of delivery receipts: Delivery documents with physical or electronic signatures and clear arrival and departure timestamps recorded by warehouse personnel.

When an invalid bill arrives, compile these records into a chronological dispute packet citing governing tariff rules.

Frequently asked questions

What is the main difference between demurrage and per diem?

Demurrage is a storage charge for a loaded container that stays inside a terminal past its free time. Per diem is an equipment charge from the shipping line for its container being outside the terminal past free days. They run on different clocks and are billed by different parties, so check both tariffs.

Why do ocean lines call per diem detention?

In many ocean tariffs, detention is another word for per diem: the line is charging for its equipment being kept away from its pool. Trucking companies use detention for driver waiting time, which is a different charge. Always read who is billing and for what.

Can I bill driver waiting time and per diem on the same invoice?

Yes, as separate line items with clear labels. Waiting time is your charge for the driver and truck, and per diem is a pass-through of the line's charge. Label them so a customer does not think they are paying twice for the same delay.

Who pays chassis usage and split fees?

The chassis pool normally bills the trucker. Whether you pass the cost on depends on your customer agreement, so state chassis and split fees in your rate sheet.

What evidence do I need to dispute a charge?

Interchange receipts, appointment logs showing no slots, terminal closure notices, return bulletins, GPS records and signed delivery receipts. The more of them carry timestamps, the stronger the dispute.

Where Dispatch Board fits

Dispatch Board keeps the pieces of this puzzle in one place. Container tracking through Terminal49 gives you availability and last free day, per diem is recorded by day with a reason for each charged day, and a dispute letter to the line goes out with the supporting events, appointments and closures. A chassis bill checker compares DCLI, TRAC and Flexi-Van invoices with your own records.

Driver waiting time is covered too: the waiting-time audit uses GPS pings inside the geofence and wait documents, and the driver app captures photos and signed PODs offline. You can try it free for 14 days.

This guide is general information from the Dispatch Board team, not legal, tax or accounting advice. Rules and rates change: confirm against the official source linked in the text before you rely on them.