Demurrage and Detention: When the Invoice Isn't Payable

Updated 2026-09-02

Demurrage is what an ocean carrier or terminal charges while your container sits inside the terminal past its free time. Detention — often called per diem — is what they charge while the container or chassis is outside the terminal, in your possession, past its free days.

That distinction is the easy part. The part worth knowing is that since 2024 a demurrage or detention invoice has to meet a federal standard to be enforceable at all, and an invoice that misses it is one you are not obliged to pay.

Two ways an invoice stops being payable

Both come from the Federal Maritime Commission’s billing rule, in force since May 28, 2024.

It arrived late. 46 CFR 541.7 gives the biller thirty days: “A billing party must issue a demurrage or detention invoice within thirty (30) calendar days from the date on which the charge was last incurred.” Miss it, and “the billed party is not required to pay the charge.” The same thirty-day clock applies to an NVOCC passing a charge down the chain, and to a corrected invoice after the wrong party was billed first.

It is incomplete. This is the broader of the two. 46 CFR 541.5 is a single sentence:

“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.”

Any of it. Not most of it.

What the invoice has to contain

46 CFR 541.6 sets the minimum in four groups. Read it as a checklist, because that is how 541.5 makes it operate.

Group	Required, at a minimum
Identifying	Bill of lading number(s); container number(s); for imports the port(s) of discharge; and “the basis for why the billed party is the proper party of interest and thus liable for the charge”
Timing	Invoice date; invoice due date; allowed free time in days; free time start date; free time end date; for imports the container availability date; for exports the earliest return date; and “the specific date(s) for which demurrage and/or detention were charged”
Rate	Total amount due; the applicable rule the daily rate rests on — tariff name and rule number, terminal schedule, service contract number and section, or negotiated arrangement; and the specific rate or rates
Dispute	Contact details for questions or a mitigation request; “digital means, such as a URL address, QR code, or digital watermark” pointing to a page describing what a request must contain; and defined timeframes for making and resolving one

There is a fifth requirement that is easy to skim past and hard to satisfy. Under 541.6(e) the invoice must carry statements from the billing party that the charges are consistent with the Commission’s demurrage and detention rules, and that “the billing party’s performance did not cause or contribute to the underlying invoiced charges.”

That second certification is the interesting one. A terminal that could not take the box back, or a carrier whose own appointment system was the reason the container sat, is certifying something on every invoice it issues.

Your thirty days to dispute

46 CFR 541.8 runs the clock the other way. The billing party “must allow the billed party at least thirty (30) calendar days from the invoice issuance date to request mitigation, refund, or waiver,” and once it receives one it “must attempt to resolve the request within thirty (30) calendar days of receiving such a request or at a later date as agreed upon by both parties.”

So the minimum shape is thirty days for the biller to invoice, thirty for you to dispute, thirty for them to answer.

What to do when the invoice lands

Check the issue date against the date the charge stopped running. More than thirty days and 541.7 says you are not required to pay it. This is a date comparison, not a judgement call.
Run 541.6 as a checklist. Start with the field the rest of the check depends on: “the specific date(s) for which demurrage and/or detention were charged.” An invoice that cannot tell you which days it is billing for cannot be checked against your own free time.
Look for the two certifications in 541.6(e). They are required content, so their absence is a 541.5 problem like any other.
Dispute in writing inside your thirty days, and note the date — their thirty-day clock to respond starts when they receive it.

Put the invoice date, the last-charge date and the missing fields in the same email. You are not arguing about whether the container was late; you are pointing at a rule with a number.

Three clocks people mix up

The words collide, and using the wrong one loses the argument before it starts.

Term	Where the box is	Who charges it
Demurrage	Inside the terminal, past free time	Ocean carrier or marine terminal operator
Detention / per diem	Outside the terminal, in your possession, past free days	Ocean carrier, for the equipment
Driver detention	A driver waiting at a gate or dock	Your drayage carrier, under your contract with them

Only the first two are what part 541 is about. Driver detention is the truckload sense of the word — a contract term between you and the carrier, with no FMC rule behind it. That is detention fees, and it is a different page for a reason.

One container can accrue all three in a week, billed by three different parties.

Who this actually applies to

46 CFR 541.2 scopes it: the part governs “any invoice issued by an ocean common carrier, marine terminal operator, or non-vessel-operating common carrier for the collection of demurrage or detention charges.” It does not govern billing between carriers and terminals themselves.

So this is ocean freight. If a dry van is sitting at a dock in Ohio, none of the above applies — check your rate confirmation instead.

What this does not do

It does not make the charge illegal. 541.7 and 541.5 make a defective invoice unenforceable against you. They do not void the underlying charge, and nothing stops a biller issuing a correct invoice inside the window. Do not read “not required to pay” as “the charge was never owed.”

It is not a rate cap. Part 541 governs what an invoice must say, not what a day may cost. Demurrage rates are tariff- and terminal-specific and may rise the longer the container sits; the rate that applies to your box is in the tariff or service contract the invoice is required to name.

FAQ

What is the difference between demurrage and detention? Where the container is. Demurrage runs while it is inside the terminal past free time; detention, often called per diem, runs while it is outside the terminal in your possession past its free days. Both are charged by the ocean side. A third thing shares the name — driver detention, a truckload contract term for a waiting driver — and it is governed by your agreement, not by 46 CFR part 541.

Do I have to pay a demurrage invoice that arrived late? Not if it arrived more than thirty calendar days after the charge stopped accruing. 46 CFR 541.7 requires issuance “within thirty (30) calendar days from the date on which the charge was last incurred”, and states that otherwise “the billed party is not required to pay the charge.” Check the issue date against the last-charge date before anything else.

What has to be on a demurrage invoice? Four groups of content under 46 CFR 541.6 — identifying, timing, rate and dispute information — plus certifications that the charges comply with FMC rules and that the biller’s own performance did not cause them. The table above lists the minimum fields.

How long do I have to dispute a demurrage charge? At least thirty calendar days from the invoice issuance date, under 46 CFR 541.8, and the billing party must then attempt to resolve your request within thirty days of receiving it. “At least” is the floor — your service contract may give longer.