Detention invoice: the two dates it does not have to carry

Two invoices arrive for the same container and the desk assumes one of them is a duplicate. They are not. One is for the box sitting inside the terminal; the other is for the box being outside it. The first is a demurrage invoice. The second is this one, and it is the half that most desks have never read field by field, because the amount is usually smaller and the sender is usually the line you deal with every week.

What it bills

A detention invoice charges you for time the carrier’s equipment was out of the carrier’s system. The meter starts when the box leaves the terminal (gate-out) and stops when the empty is accepted back at the nominated depot (empty container return). In between, your yard, your warehouse and your haulier’s queue are all on the line’s clock.

That is the whole of the difference. US law does not define detention separately from demurrage at all. It defines them in one sentence, as

any charges, including “per diem” charges, assessed by ocean common carriers, marine terminal operators, or non-vessel-operating common carriers related to the use of marine terminal space (e.g., land) or shipping containers, but not including freight charges.

Marine terminal space is demurrage. The shipping container is detention. The asset decides which word goes on the invoice, and nothing else does, which is why the same billing rules, the same required fields and the same thirty-day deadlines govern both.

The two dates it does not have to carry

Here is the gap worth knowing before the next one lands.

The required minimum information on a detention invoice is specific and long. On timing it covers the invoice date and due date, “the allowed free time in days”, the start date and the end date of free time, the container availability date on an import, the earliest return date on an export, and “the specific date(s) for which demurrage and/or detention were charged”.

Read that list again against the clock it is billing. Gate-out is not in it. The empty return is not in it. The two events that begin and end a detention charge are the two events the invoice is not required to show you.

What you get instead is the free-time window and an assertion of which days were charged. Whether those days actually sit between your gate-out and your empty return is something only your own records can answer: the equipment interchange receipt at the gate, and the receipt from the depot that took the box back. A detention invoice is therefore checked from the outside in: start with your two dates, then see whether the line’s billed days fall inside them.

How a detention charges calculation actually runs

A detention charges calculation is four numbers, and only two of them are on the invoice.

1. The start. The day the box passed the terminal gate, from your equipment interchange receipt.
2. The free days. The allowed free time in days, which the invoice must state, counted on the basis the tariff or contract sets.
3. The end. The day the depot accepted the empty, from the depot’s receipt.
4. The rate per tier. Detention is rarely one rate. The invoice has to carry the rate for each tier and the days charged in each, so a fourteen-day overstay can span two or three rates.

Chargeable days are the days between the start and the end, less the free days, priced tier by tier. The arithmetic is trivial. The sourcing is not: steps one and three come from your own paperwork, because the rules do not make the line print either date. So a detention charges calculation done from the invoice alone is checking the carrier’s figures against the carrier’s own assertion of the dates.

One thing the calculation must not quietly absorb: a day the box sat inside the terminal is demurrage, not detention. If the billed days start before gate-out, the line has billed storage at an equipment rate. See dwell time for why one container carries several different day counts at once.

What else has to be on it

The rate line is the one that quietly matters most. The invoice has to name “the applicable detention or demurrage rule” the daily rate is based on, and the rule lists the four places it can live: the tariff name and rule number, the terminal schedule, the service contract number and section, or a negotiated arrangement. Three of those four you can read. The fourth you cannot, unless your own company signed it. So a line citing a service contract section is citing a document only your file holds, and the free-time figure it asserts is checkable in exactly one place.

Missing a field is not a discount

The consequence of an incomplete invoice is unusually blunt for a billing regulation:

Failure to include any of the required minimum information in this part in a demurrage or detention invoice eliminates any obligation of the billed party to pay the applicable charge.

Not reduced. Eliminated. And it applies field by field, which is why the table above is worth running down on the day an invoice arrives rather than on the day somebody questions it.

The timing rules work the same way. The line has thirty calendar days from the date the charge was last incurred to issue the invoice, and if it does not, “the billed party is not required to pay the charge”. An NVOCC billing you for detention gets its own thirty days from the date of the invoice it received, which is how a detention charge can reach you months after the box went back and still be inside the rules, and also how it can fall outside them. If the line billed the wrong company first, the corrected invoice still has to be out inside thirty days of the charge last accruing; the clock runs from the charge, not from the correction.

When the empty cannot go back

Detention exists to get the box returned. When returning it is impossible, the charge stops doing the job it is there to do, and the regulator says so directly:

Absent extenuating circumstances, practices and regulations that provide for imposition of detention when it does not serve its incentivizing purposes, such as when empty containers cannot be returned, are likely to be found unreasonable.

A depot that is full, a return appointment that cannot be booked, a lane the line has suspended: each is a reason the charge may not stand, and each is only as good as the record of it. The depot, the date, the time, the appointment reference and the name of whoever refused the box: captured on the day, that is evidence. Reconstructed six weeks later from memory, it is an argument.

Why the names are such a mess

If this all feels harder than it should be, the Commission has noticed too. In weighing whether a practice is reasonable it may consider “the extent to which the definitions differ from how the terms are used in other contexts”, a polite way of recording that the industry uses one word for several charges and several words for one. Per diem is the clearest case: on the container it is detention under another name, and on a chassis it is not covered by these rules at all. Two lines, identical spelling, different rights.

The practical consequence for a desk is that you cannot sort the invoices by their titles. You sort them by which asset was occupied and which clock was running, and then you check the dates the invoice did not have to print.

What a desk actually needs to hold

Every field above has to be matched against something, and almost none of it lives in one place: the gate-out is on the haulier’s interchange receipt, the empty return is on the depot’s, the free time is in the contract or the tariff, and the dates charged are on a PDF that arrived by email. Holding all of it, per container, is the job that demurrage and detention software that holds the gate dates exists to do. Not to argue the charge, but to have the two dates ready when the invoice turns up asserting a third.

If the charge is already on the table, the route after that is a charge complaint, where the burden of proving the charge reasonable sits with the party that raised it.