The Federal Maritime Commission's billing rule, 46 CFR Part 541, sets one national format for detention and demurrage invoices in US ocean freight. This page explains what the rule requires on an invoice, who must issue it and by when, how the chargeable-day and 30-day clocks are computed, and which AINumbers tools help with the surrounding billing and reconciliation work. It is written for billing teams at ocean common carriers, NVOCCs, and marine terminal operators, and for importers, exporters, consignees, and their logistics providers who receive these invoices.
Part 541 is the Federal Maritime Commission's final rule on detention and demurrage billing requirements, published at 89 FR 14362 on February 26, 2024 and effective May 28, 2024. It carries out the billing provisions that the Ocean Shipping Reform Act of 2022 added to 46 U.S.C. 41108(c). The rule fixes two things: who may be billed, and what an invoice must contain to be payable.
The core mechanic sits in § 541.5: an invoice that leaves out required information eliminates the obligation to pay it. The billed party owes nothing on a non-compliant invoice, so invoice format is a payment-risk question for the billing party and a payment-defense question for the billed party. The required contents are listed in § 541.6, organized in five groups:
| Clause | What the invoice must show |
|---|---|
| § 541.6(a)(1)-(4) | Identification: the bill of lading numbers, the container numbers, the port of discharge for imports (or the lowest port of discharge stated for exports), and the basis for asserting that the billed party is liable for the charges. |
| § 541.6(b)(1)-(7) | Timekeeping: the invoice date, the due date, the allowed free time in days, the start and end dates of free time, the date the container became available for pickup (imports) or the earliest return date (exports), and the specific dates on which each charge was incurred. |
| § 541.6(c)(1)-(3) | Money: the total amount due, the applicable rule in the carrier or terminal tariff (with the rule number), and the specific rate charged per day or period. |
| § 541.6(d)(1)-(2) | Dispute access: contact information for a billing representative, plus a direct link (URL, QR code, or watermark) to a public website that explains how to request mitigation, a refund, or a waiver, with defined timeframes. |
| § 541.6(e)(1)-(2) | Certifications: that the charges are consistent with applicable FMC rules, including the rules for detention and demurrage practices at 46 CFR 545.5, and that the billing party's own actions did not cause or contribute to the charges. |
Definitions in § 541.3 fix the vocabulary: a billing party is the ocean common carrier, marine terminal operator, or NVOCC that issues the invoice, and a billed party is the person the invoice names as responsible under the contract of carriage or terminal tariff. Scope and applicability sit in § 541.2: the part applies to the demurrage and detention rules, practices, and invoices of ocean common carriers, marine terminal operators, and NVOCCs, and it does not reach the billing relationship between a marine terminal operator and an ocean carrier. § 541.1 states the purpose and § 541.99 carries the OMB control number (3072-0073) for the information collection.
Part 541 governs invoice mechanics. Whether a charge itself is reasonable is a separate question, assessed under 46 U.S.C. 41108 and the FMC's detention and demurrage practices rule at 46 CFR 545.5, which the certification in § 541.6(e)(1) references.
The rule runs on 30-day clocks. Billing parties face issuance deadlines in § 541.7; billed parties get a dispute window, and billing parties a response duty, in § 541.8. All periods run in calendar days.
The billing party must issue the invoice within 30 calendar days after the date the charge last accrued, which for demurrage is normally the outgate date.
The billed party has at least 30 calendar days from the invoice issuance date to ask for mitigation, a refund, or a waiver.
The billing party must attempt in good faith to resolve the request within 30 days of receiving it, or within a longer period the parties agree on.
| Clause | Who | Deadline |
|---|---|---|
| § 541.7(a) | Ocean common carrier, marine terminal operator, or NVOCC issuing the invoice | Issue within 30 calendar days after the date the charge last accrued. |
| § 541.7(b) | NVOCC re-billing an invoice it received from an ocean carrier or terminal operator | Issue within 30 calendar days of the issuance date of the invoice it received. |
| § 541.7(c) | NVOCC that both receives and issues such invoices and acts on behalf of another NVOCC | Issue within 30 calendar days after notice of its dual role. |
| § 541.7(d) | Billing party that invoiced the wrong party | Issue a corrected invoice within 30 calendar days after determining the error, restarting the billed party's dispute window. |
| § 541.8(a) | Billed party | At least 30 calendar days from the invoice issuance date to request mitigation, refund, or waiver. |
| § 541.8(b) | Billing party | Attempt in good faith to resolve the request within 30 days of receipt, or longer by agreement. |
Dates that matter: the final rule was published on February 26, 2024 (89 FR 14362) and took effect May 28, 2024, so the billing requirements apply to detention and demurrage invoices issued on or after that compliance date. This page reflects the rule text as of September 2026; the current text is linked in the sources section below.
Every compliant invoice tells the same arithmetic story: free time, then chargeable days, then the 30-day clocks. The worked example below uses synthetic inputs and a flat daily rate to keep the computation readable; a real tariff can use tiered rates, and the invoice must then show the applicable rule and each specific rate under § 541.6(c).
An import container is discharged and available for pickup on Mar 4, 2026. The tariff grants 4 calendar days of combined free time, so free time runs Mar 4 through Mar 7 and free time ends Mar 7. The container is outgated on Mar 13, 2026. The chargeable period is therefore Mar 8 through Mar 13. At a synthetic flat rate of $165 per container per day:
Invoice must show: allowed free time (4 days), start and end of free time (Mar 4, Mar 7), availability date (Mar 4), each charged date (Mar 8 to Mar 13), the tariff rule, and the rate, per § 541.6(b) and (c).
The last charge accrued on the outgate date Mar 13, 2026. The billing party issues the invoice on Mar 18, 2026, inside the § 541.7(a) window. The billed party submits a mitigation request on Apr 10, 2026, inside the § 541.8(a) window.
Each date is computable from two inputs: the last accrued charge date and the invoice issuance date.
The same three computations decide most invoice disputes in practice: whether the invoice was issued inside the 30-day window, whether the free-time and chargeable-day arithmetic matches the tariff rule the invoice cites, and whether the mitigation request landed inside the dispute window. A preflight check of an invoice against this structure is arithmetic on dates and counts, which is what makes the rule machine-checkable.
AINumbers runs browser-based tools that cover the billing and reconciliation work around invoices like these. Everything below is live today, runs client-side, and transmits no data.
T104 · Receivables DSO & Collections Optimizer models aging buckets and days-sales-outstanding, the same date arithmetic that drives the § 541.7(a) issuance window and the § 541.8(a) dispute window.
T132 · Invoice-to-Payment Orchestrator structures the path from an issued invoice to settlement or dispute, and T09 · A2A Reconciliation Workbench reconciles invoice line items against payments and remittance records.
The TradeTech & Trade Finance Hub covers the wider ocean-trade document set, including Incoterms 2020 risk mapping and letter-of-credit validation, where detention and demurrage exposure originates.
The E-Invoicing, VAT & ViDA Compliance Hub tracks structured-invoice mandates, and the B2B Payments & Platform Operations Hub covers invoice-to-payment orchestration across platforms.
Invoice content compliance under § 541.6, issuance timing under § 541.7, and dispute handling under § 541.8 across a billed-book of containers.
Demurrage billing practice at the terminal level, including tariff rule citation and the public mitigation-procedures page the invoice must link to.
Checking an invoice against the rule: whether the required contents are present, whether the 30-day clocks were respected, and when to dispute.
The clause-level map of the rule for process design, vendor management, and internal audit, with a primary-source trail for each claim.
Text retrieved and cited as of September 2026. Clause citations on this page refer to 46 CFR Part 541, Subpart A.
46 CFR Part 541, Subpart A (§§ 541.1 through 541.8, and § 541.99), current electronic text, eCFR: ecfr.gov/current/title-46/part-541Retrieved September 2026 · rule effective May 28, 2024
Final rule publication: Detention and Demurrage Billing Requirements Under the Ocean Shipping Reform Act of 2022, 89 FR 14362 (February 26, 2024): federalregister.gov/citation/89-FR-14362Published February 26, 2024
Statutory basis: 46 U.S.C. 41108(c), added by the Ocean Shipping Reform Act of 2022: law.cornell.edu/uscode/text/46/41108Current statute
Cross-referenced practice rule: 46 CFR 545.5 (unfair or unreasonable rules and practices), referenced by § 541.6(e)(1): ecfr.gov/current/title-46/section-545.5Current electronic text
Last Reviewed · September 2026 · 46 CFR Part 541 · Effective May 28, 2024