Demurrage, per diem and detention are three bills from three different companies

Who is charging you, in each case

Demurrage comes from the marine terminal. Your container is occupying ground inside a facility with finite space, past the free time that facility allows. The terminal wants the ground back, and the charge is the pressure it applies.

Per diem comes from the ocean carrier, the shipping line whose name is on the box. That container is an asset they need back in circulation. The clock starts when the box leaves the terminal and it does not stop when the box reaches your dock. It stops when the empty is returned.

Detention is the one people mean least precisely. In drayage as it is actually spoken in Miami, detention is the trucker's time: a driver arrived, the free waiting window elapsed, and the driver is still sitting there. The ocean carrier's tariff may also use the word for equipment held past free time, which is why the same word can appear on two invoices meaning two things. When you get a bill, read who sent it before you read the word.

The clocks overlap, and that is how a bill gets ugly

Picture a container that misses its last free day by four days, then gets delivered, then sits on your yard for a week before the empty goes back.

For those four days, demurrage runs at terminal rates. The moment the box goes out the gate, demurrage stops and per diem starts, and per diem keeps running through the delivery, through the unload, and through the week the empty sat waiting for a return appointment. If the driver waited at your dock beyond the free window on delivery day, detention is on that day's invoice too.

One container, three charges, three parties, and only the first of them was stopped by pulling the box. That is the sentence worth remembering: a pre-pull stops demurrage, and only demurrage.

What stops each one

Demurrage stops when the container leaves the terminal. That is the whole mechanism, which is why pre-pulling is a real lever rather than a sales pitch.

Per diem stops when the empty container is returned to the line. Not when it is unloaded, not when it is on your yard, not when it is empty in your parking lot. Returned. This is the one that surprises importers most, because the freight is finished and the cost is not. Transloading is the direct answer: move the cargo onto a trailer, return the box early, and the long inland leg runs without the shipping line's equipment attached to it.

Detention stops when the driver leaves. Drop and pick avoids it entirely by removing the waiting: the container is left, the driver goes, and it is collected later. Live unload is what generates it.

The 2024 rule changed who can bill you, and when

This part is genuinely useful and most people importing into Miami have never been told it. The Federal Maritime Commission's billing rule took full effect on 28 May 2024, and it constrains demurrage and detention invoices in ways that are worth knowing before you pay one.

Invoices have a deadline. Vessel-operating carriers and marine terminal operators must issue a demurrage or detention invoice within 30 calendar days of the day the charges last accrued. A non-vessel-operating carrier passing one along has 30 days from the date of the invoice it received. An invoice that turns up months later is not automatically valid.

The bill can only go to one of two parties: the person who contracted with the billing party for the transportation or storage, or the consignee, meaning the ultimate recipient of the cargo. It cannot be issued to several parties at once and left for them to argue about.

You get at least 30 calendar days to request mitigation, a refund or a waiver, and if you make that request in time, the billing party has to try to resolve it within 30 days unless you both agree to longer.

None of that makes a legitimate charge disappear. What it does is turn a charge you thought was final into a conversation with a defined process and a clock of its own.

What to do when the invoice arrives

Read the header before the number. Which company sent it decides which of the three charges it can possibly be, and that decides what could have prevented it.

Check the dates against the rule. When did the charges last accrue, and when was the invoice issued? More than 30 days apart is a question worth asking in writing.

Check the charge against the event. Demurrage after gate-out is not demurrage. Per diem before gate-out is not per diem. Both happen on real invoices, usually because a date got keyed from the wrong milestone.

Then ask the harder question, which is what decision made the charge inevitable. Almost every large accessorial bill traces back to a choice made about a day too late, and the fix is upstream rather than in the dispute.