The FMC demurrage and detention billing rule, codified at 46 CFR Part 541, does something almost no other freight regulation does: it lists the exact contents a demurrage or detention invoice must carry, and then says that leaving any of them out eliminates the obligation to pay. The invoice requirements sit in 46 CFR 541.6, grouped into identifying information, timing information, rate information, dispute information, and two certifications from the billing party. The consequence sits one section earlier, in 46 CFR 541.5: “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.”
That is a stronger position than shippers usually have on any accessorial. Most dwell charges are contractual, argued from a rate agreement and whatever timestamps you can assemble. Container demurrage and detention are different. There is a federal rule, it is specific, and a lot of invoices in circulation do not satisfy it.
This post walks the rule section by section, gives you the field-by-field audit checklist, and then says plainly where the rule stops helping, because overstating it will cost you credibility with a carrier that knows the regulation better than you do.
What Part 541 covers, and what it does not
Scope first, because this is where most of the misapplication happens.
Part 541 applies to invoices issued by ocean common carriers, marine terminal operators, and non-vessel-operating common carriers for the collection of demurrage or detention charges. It expressly does not govern the billing relationships among and between ocean common carriers and marine terminal operators, so a terminal invoicing a steamship line is outside it.
46 CFR 541.3 defines the terms that carry the weight:
- Demurrage or detention means 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 or shipping containers, but not including freight charges.
- Billing party is the ocean common carrier, marine terminal operator, or NVOCC issuing the invoice.
- Billed party is the individual or entity receiving the invoice who bears responsibility for payment.
- Demurrage or detention invoice means any statement of charges printed, written, or accessible online that documents an assessment of demurrage or detention charges. An online portal screen counts.
Note what that definition captures and what it does not. It captures container-side dwell charges, including ones labeled per diem, when the party assessing them is a carrier, NVOCC, or terminal. It does not reach a truckload carrier’s detention charge for holding a driver and tractor at your dock, which remains purely contractual and is argued the way a detention claim at a facility with no gate system is argued. Do not cite Part 541 at a dry van carrier. It will not land, and it signals that you are quoting a rule you have not read.
Who can legally be billed
46 CFR 541.4 narrows the field of permissible recipients to two, and forbids billing both.
A properly issued invoice goes either to the person for whose account the billing party provided ocean transportation or storage of cargo and who contracted for those services, or to the consignee. If the billing party invoices the first, it cannot also invoice the second. And it cannot issue an invoice to any other person at all.
This is a live audit test, not a technicality. If your customs broker, your drayman, and you all receive an invoice for the same container-days, at most one of those is a properly issued invoice. If you are a beneficial cargo owner receiving a demurrage invoice for a container you never contracted to move and are not the consignee of record, the threshold question is whether you are a permissible billed party at all, which comes before any argument about whether the days are right.
The 30-day issuance deadline
46 CFR 541.7 sets the clock that catches the most invoices.
A billing party must issue a demurrage or detention invoice within 30 calendar days from the date on which the charge was last incurred. Miss that and, by the terms of the rule, the billed party is not required to pay the charge.
Three details matter in practice.
The clock runs from the last day the charge was incurred, not from the day the container was returned, not from the day the terminal closed its books, and not from the day someone in accounts receivable noticed. If the last demurrage day on a container was March 3, the invoice has to be out by April 2.
NVOCCs get a different starting point. For an NVOCC, the 30 days run from the issuance date of the demurrage or detention invoice it received, rather than from when the charges accrued. That is a pass-through allowance, not an extension of the underlying clock, and it means the upstream invoice date is a document you can ask for.
A misdirected invoice can be corrected, but only inside the original window. If the billing party invoiced the wrong recipient, it may issue a corrected invoice to the proper party, and that corrected invoice still has to land within 30 days of when the charge was last incurred. An invoice that arrives on day 55 with an apology about billing the wrong entity does not get a fresh 30 days.
There is also a dispute pass-through provision for an NVOCC that is both a billing party and a billed party. When such an NVOCC notifies its own billing party of a dispute, that billing party must give the NVOCC an additional 30 calendar days to dispute the charge.
The invoice contents checklist
This is the section to keep. Run any demurrage or detention invoice against the twenty items below. They come from 46 CFR 541.6, which requires the invoice to be accurate and to contain, at a minimum, each of the following.
| Group | Required field |
|---|---|
| Identifying | Bill of lading number(s) |
| Identifying | Container number(s) |
| Identifying | Port(s) of discharge, for imports |
| Identifying | The basis for why the billed party is the proper party of interest and thus liable |
| Timing | Invoice date |
| Timing | Invoice due date |
| Timing | Allowed free time in days |
| Timing | Start date of free time |
| Timing | End date of free time |
| Timing | Container availability date, for imports |
| Timing | Earliest return date, for exports |
| Timing | The specific date(s) for which demurrage or detention were charged |
| Rate | Total amount due |
| Rate | The applicable demurrage or detention rule the daily rate is based on (tariff name and rule number, terminal schedule, service contract number and section, or negotiated arrangement) |
| Rate | The specific rate or rates per that tariff rule or service contract |
| Dispute | Contact information for questions or a request for fee mitigation, refund, or waiver |
| Dispute | Digital means (URL, QR code, or digital watermark) pointing to a public page describing what documentation a mitigation, refund, or waiver request requires |
| Dispute | Defined timeframes, compliant with Part 541 billing practices, for requesting mitigation and for the billing party to resolve the request |
| Certification | A statement that the charges are consistent with the FMC’s demurrage and detention rules, including Part 541 and 46 CFR 545.5 |
| Certification | A statement that the billing party’s performance did not cause or contribute to the underlying invoiced charges |
Four of these are the ones invoices actually miss.
The proper party of interest basis. Not the name of the billed party, which every invoice has. The stated basis for why that party is liable. Many invoices simply address a company and stop.
Free time start and end dates. An invoice that shows charged days but never states when free time began and ended gives you no way to check the arithmetic, which is exactly what the section exists to prevent.
The rule the rate comes from. A dollar figure with no tariff name, rule number, or service contract section is not a rate citation. This is the field that lets you go read the rule and find out whether the rate was applied correctly.
The digital means for mitigation requests. A generic “contact us” line is not a URL, QR code, or digital watermark pointing to a page that describes required documentation. This one is missing constantly and is trivially verifiable.
The dispute window and the resolution obligation
46 CFR 541.8 sets two deadlines running the other direction.
The billing party must allow you at least 30 calendar days from the invoice issuance date to request mitigation, refund, or waiver. And if you make such a request, the billing party must attempt to resolve it within 30 calendar days of receiving it, or later if both parties agree.
Read those with 541.6(d)(3) in hand. The invoice itself must state defined timeframes that comply with these practices. So an invoice giving you a 10-day window to dispute is not merely inconvenient, it is stating a timeframe that does not comply, which is a contents problem as well as a practices problem.
Two habits follow. Put your mitigation request in writing, dated, to the contact named on the invoice, so the 30-day resolution clock has a start you can prove. And calendar day 31. Silence past that date is itself a fact worth citing.
Where the rule stops helping
Now the honest part, because a shipper who overreads Part 541 loses the argument and the relationship.
“Eliminates any obligation to pay” is the rule’s text, not a self-executing refund. A billing party that agrees the invoice was defective will usually cancel and reissue if it can still do so inside the deadlines. One that disagrees will keep invoicing, and your recourse runs through the Federal Maritime Commission’s complaint and charge-complaint processes, not through a line in your AP system. Withholding payment is a commercial decision with commercial consequences: holds on releases, credit terms, and future bookings. Make it deliberately.
Accuracy is a separate requirement from completeness. An invoice can carry all twenty fields and still be wrong about the container availability date. The fields exist so you can check the substance. Do not let a compliance checklist replace the arithmetic.
Part 541 is not the whole of FMC demurrage and detention regulation. The certification in 541.6(e)(1) references 46 CFR 545.5, the Commission’s interpretive rule on unreasonable demurrage and detention practices. Whether a charge served its incentive purpose is a different question from whether the invoice was complete, and it is a harder one.
Nothing here touches inland detention. Truckload detention, layover, and driver dwell are contract charges under a rate confirmation. The evidence-first approach for those is in what documents actually win a detention dispute and how to dispute a detention charge with no in and out times on the POD.
How to run this at the audit desk
The rule is only worth what your process extracts from it. Six steps, in order.
- Timestamp every demurrage and detention invoice on arrival. You need the received date to run any of the clocks, and portal-only invoices need a capture date recorded when someone downloads them.
- Screen for the 30-day issuance deadline first. It is one subtraction: last charged date to invoice date. It disposes of an invoice faster than any contents review, so run it before you read anything else.
- Check that you are a permissible billed party. Are you the contracting party or the consignee? Did anyone else in the chain get the same invoice for the same container-days? Duplicate exposure across parties is the container-side cousin of the pattern described in catching duplicate freight invoices.
- Run the twenty-field checklist and record which fields are missing, by section reference. “Missing 541.6(a)(4) and 541.6(d)(2)” is a sentence a carrier’s billing team can act on. “Your invoice is incomplete” is not.
- Verify the arithmetic against the free time start, free time end, and charged dates now that the invoice is required to state them. Then verify the rate against the tariff rule or service contract section the invoice cites.
- Send the mitigation request in writing within the stated window, list the missing fields with citations, state the arithmetic you dispute, and calendar the 30-day resolution deadline.
What good looks like
A demurrage invoice you cannot dispute has all twenty fields, arrived inside 30 days of the last charged day, went to exactly one properly billed party, cites a tariff rule you can look up, and shows free time dates that reconcile to the terminal’s container availability. When you get one of those, pay it. Getting the process right means paying the good invoices quickly and putting the argument only where the rule actually gives you one.
The reason to build the checklist anyway is volume. A single defective demurrage invoice is worth a few hundred dollars of attention at most. A billing pattern that omits the free time dates on every invoice for a year is worth building a process around, and the same is true of the equipment-side charges that arrive alongside it, sorted out in auditing chassis per diem and split charges in the drayage dwell stack. Deadline discipline across all of it is collected in every freight billing deadline that can cost you money.
Sources
- 46 CFR Part 541, Demurrage and detention billing requirements (Cornell LII)
- 46 CFR 541.3, Definitions (Cornell LII)
- 46 CFR 541.4, Properly issued invoices (GovInfo, CFR 2025 annual edition)
- 46 CFR 541.5, Failure to include required information (Cornell LII)
- 46 CFR 541.6, Contents of invoice (Cornell LII); full enumerated text verified at GovInfo CFR 2025, section 541.6
- 46 CFR 541.7, Issuance of demurrage and detention invoices (Cornell LII)
- 46 CFR 541.8, Requests for fee mitigation, refund, or waiver (Cornell LII)