What last free day actually costs you

Ask a brokerage owner what demurrage cost them last quarter and you will usually get a shrug and a guess. Not because nobody is paying attention — because the charge does not arrive attached to anything. It shows up weeks later on a steamship line statement, gets coded to port charges, and never touches the load it belongs to. The margin on that load still reads fine in the report.

This is the mechanism worth understanding, because once demurrage is a number on a load it stops being a mystery and starts being a decision.

Demurrage and per diem are not the same charge

They are routinely used as if they were interchangeable, and they are not.

Demurrage is charged while the container is still inside the terminal past its free time. You are occupying the terminal's ground. It is assessed under the tariff of whoever issued your bill of lading — the ocean carrier, or the NVOCC if you are holding a house bill.

Per diem — often called detention on the ocean side — is charged once the container is out of the terminal and in your possession past its allotted free days. You are holding the line's equipment. The clock runs until the empty is ingated and receipted, not until your driver drops it at the gate.

Two clocks, two different triggers, and they hand off to each other. Get the box out on time and you kill demurrage — then start per diem the moment the wheels turn.

There is a third charge that hides between them. At some ports the marine terminal assesses its own storage on the box, separately from the line's demurrage. Two invoices, two parties, same days, same container. If you have only ever budgeted for one of them, check a recent statement.

And a fourth, which is not the line's at all: the chassis under the box is rented by the day from a pool or a leasing company, and its clock runs from outgate to termination including weekends. A container sitting at a consignee for four days is accruing per diem to the ocean carrier and chassis rental to the pool at the same time, from two unrelated tariffs.

How the clock actually works

Free time starts from availability, not from the arrival notice. The notice gives you an ETA that is frequently stale by the time you read it; the terminal gives you the discharge date and the date the box is actually appointable. Those are different dates, and the second one is the one that matters.

From there:

• Free time is counted in calendar days or working days depending on the tariff. Assuming calendar days when the tariff says working days, or the reverse, will move your last free day by a weekend.
• The rate is almost always tiered. The first band of days is cheaper than the second, and the second than the third. Four days late is not four times one day late — it is whatever the tariff schedule says, which escalates. The schedule lives on the carrier's tariff or its free-time page, not on the arrival notice.
• Holds do not stop the clock, at least not by default. A customs exam, a freight hold, a line hold or an unpaid terminal fee can make the box impossible to retrieve while demurrage continues to accrue against it. This is the single most common source of a demurrage bill nobody thinks they earned.
• Appointment scarcity is the same problem in a different coat. A last free day three days out is worth nothing if the terminal has no appointment slots inside those three days. The clock does not care that you tried.

Because holds and appointment scarcity are so common, disputes are worth taking seriously. The Federal Maritime Commission has rules governing demurrage and detention billing: who may be billed, the window in which an invoice must be issued after charges stop accruing, the data elements the invoice has to contain, and the time a billed party has to request mitigation. Read the current rule text rather than a summary — but know that an invoice missing required elements, or issued outside the window, is not automatically something you have to pay.

Whether you win a dispute is largely a question of evidence you either kept or did not: the appointment attempts, the hold status on the day, the date the box actually became available, the empty return receipt. None of that can be reconstructed six weeks later from memory.

Why absorbed demurrage is invisible in most books

Follow the money on a normal drayage move where four days of demurrage got incurred.

The box cannot be released until the line is paid. So the brokerage fronts it — an advance — to get the container moving. The cash leaves as a payment to the steamship line. When the line's statement arrives, the charge is reconciled against the payment and closed. At no point in that sequence does anything write four days of demurrage onto the load, with a cause and a party who should have paid it.

The consequences follow from that one omission:

• Per-load margin is wrong, and wrong in the flattering direction. The revenue and the carrier cost are on the load; the demurrage is in an expense account. Every profitability report built on load-level margin is overstating that lane.
• Nobody decided to absorb it. Absorption happened by default. A brokerage that decides to eat a charge to keep a customer is making a commercial choice; a brokerage that eats it because no one matched the invoice back to a container is making no choice at all.
• The rebillable ones never get rebilled. Plenty of demurrage is genuinely the customer's — their customs broker filed late, their consignee could not take delivery, they sat on the delivery order. That is a charge you are entitled to pass through, and you cannot pass through a charge you never recorded.
• The pattern never surfaces. One customer whose paperwork is always late will produce demurrage every month, on every box, and nobody will ever see it as a pattern, because it never accumulated anywhere you could sort it.

What to do about it

None of this requires new software to understand. It requires the charge to become data.

Record availability and last free day as fields on the load, not as a note. A date in a remarks box cannot be sorted, cannot be alerted on and cannot be reported. A date in a field can be a worklist ordered by days remaining, which is what a drayage desk actually needs at eight in the morning.

Take the last free day from the terminal, not the arrival notice. And record where you got it and when, because that becomes the evidence if you dispute.

Write the charge onto the load the day it is incurred, with a bill-to party. Not when the statement arrives. The bill-to decision follows the cause: the customer's delay is the customer's charge, your dispatch failure is yours, a carrier who missed the appointment is a chargeback against the carrier. If you intend to absorb it, record it billed to yourself and mark it written off — with a name against the write-off.

Reconcile the line's statement back to containers. Every charge on that statement belongs to a box, and every box belongs to a load. If a charge cannot be matched, that is the finding, not an inconvenience.

Keep the empty return receipt. Per diem stops when the empty is receipted. If the line's system did not register the return, the receipt is the only thing standing between you and paying for days after the box was gone.

Do those five things and demurrage stops being an unpleasant surprise on a statement. It becomes what it always was: a per-day cost with a cause, an owner and a decision attached.