Port congestion is usually discussed as a capacity problem. For the teams that pay the bills, it is a billing problem that shows up three to six weeks later. Every day a container sits past free time because an appointment was unavailable or a terminal closed becomes a line item on a demurrage or detention invoice.

The conditions this month are about as bad as they get. Port congestion reached new highs in September amid an extended peak (Seatrade Maritime), and September is expected to be the busiest import month of the year at 2.31 million TEU (NRF). More boxes, fewer appointments, longer dwell: the invoices that follow are predictable.

What is less predictable is whether your team will be able to dispute the ones that should not be paid.

Why does congestion turn into D&D invoices?

Free time is the number of days a container can sit at the terminal (demurrage) or stay out with the importer (detention) before charges start. Congestion eats free time from both ends:

• Appointments disappear. A trucker cannot pick up a box the terminal will not release a slot for, so demurrage accrues on a container nobody could have moved.
• Terminals close or restrict gates. Weather, labor and yard density all shorten the working window.
• Empties cannot be returned. When return locations are full or change without notice, detention runs on equipment the importer is trying to give back.
• Cargo gets rolled. A late vessel compresses arrivals into the same week, and rolled bookings and schedule changes push multiple containers into the same congested window.

None of these are the importer's fault, and many of them are disputable. But a dispute is only as strong as the evidence behind it.

What the FMC billing rule actually gives you

The Federal Maritime Commission's Demurrage and Detention Billing Requirements rule took full effect on May 28, 2024 (FMC). The provisions that matter most for dispute teams:

• Invoices must include minimum information (container, free time, dates, rates, how to dispute) — What it means operationally: An incomplete invoice is itself a basis to push back
• Carriers and terminals must issue invoices within 30 calendar days of when charges were last incurred — What it means operationally: Late invoices do not have to be paid
• The billed party has at least 30 days from the invoice to request mitigation, refund or waiver — What it means operationally: Your clock starts on invoice receipt, not when someone opens it
• The billing party must attempt to resolve disputes within 30 days of receiving them — What it means operationally: A dispute that is filed on time and documented forces a response

One caveat worth knowing: in September 2025, the D.C. Circuit set aside the section of the rule that specified who may be billed (World Shipping Council v. FMC). The invoice content, timing and dispute provisions were not vacated, but the question of which party can be invoiced is less settled than it was. That makes it more important, not less, to check every invoice you receive.

Why most dispute queues lose

The rule gives importers, forwarders and brokers leverage. Most teams leave it on the table for three reasons:

The evidence is scattered. Proof that an appointment was unavailable lives in a portal screenshot, a trucker's email, or a dispatcher's note. Proof of a terminal closure lives in an advisory email nobody saved. Assembling it for one container takes 20 to 40 minutes; for a vessel's worth of containers it takes days.

The invoices arrive in a pile. Congestion does not produce one invoice, it produces dozens in the same week, often after the busiest operational stretch. The dispute window runs while the team is still catching up.

Nobody checks the math. Free-time calculations, rate tiers and the dates on the invoice are rarely reconciled against what actually happened. This is the same pattern behind freight invoice errors that cost operations six figures a year: nobody compares the bill to the record because there is no time to.

How should you handle a D&D dispute queue during peak?

You should treat every D&D invoice as a reconciliation task with a deadline: check it against free time and the event record within days of receipt, pull the evidence automatically from email and portal history, and file disputes well inside the 30-day window. Waiting until someone has time guarantees that the disputable charges get paid.

In practice, that breaks into four steps.

1. Log the invoice and start the clock. Record receipt date, container numbers, billing party and the dispute deadline the moment the invoice lands.
2. Validate the invoice. Does it contain the required information? Was it issued within 30 days of the last charge? Do the free-time start and end dates match the discharge, availability, pickup and return events?
3. Assemble the evidence. Pull every email, advisory and appointment attempt tied to that container: "no appointments available" replies, terminal closure notices, empty-return location changes, rolled-booking notices.
4. Draft and file the dispute. A short, specific request citing dates and attaching evidence, sent to the billing party's designated dispute contact, with the 30-day resolution window tracked.

Steps 1, 2 and 3 are where time goes, and all three are mechanical.

Where AI agents fit

This is a document-and-inbox problem, which makes it a good fit for AI agents working inside the channels your team already uses.

Evidence capture happens in real time, not after the invoice. An agent coordinating drayage during port congestion already sees the appointment requests, the rejections and the trucker updates. Tagging each of those to the container as it happens means the dispute file exists before the invoice does.

Invoice checks run on arrival. The agent reads the invoice from email, extracts containers, dates and charges, compares them to free time and the event log, and flags discrepancies: charges for days the terminal was closed, detention accrued after a documented return attempt, invoices issued past the 30-day limit.

Disputes get drafted inside the window. For flagged invoices, the agent drafts the dispute with the timeline and evidence attached and routes it to a person for approval. Your team reviews and sends; it does not reconstruct.

Recoveries get tracked and billed. Where a charge is valid but belongs to the shipper under contract, the same logic that drives accessorial capture for detention billing makes sure it is passed through instead of absorbed.

A realistic outcome is not "no D&D." Some charges are legitimate. The outcome is that every disputable charge gets disputed, on time, with evidence, and every pass-through charge gets billed.

Frequently asked questions

What is the difference between demurrage and detention? Demurrage is charged for containers that stay at the terminal past free time. Detention is charged for carrier equipment kept outside the terminal past free time, including late empty returns.

How long do I have to dispute a D&D invoice under the FMC rule? The billed party has at least 30 days from the invoice to request mitigation, refund or waiver, and the billing party must attempt to resolve the dispute within 30 days of receiving it. Check your specific invoice, since billing parties can offer longer windows.

Do I have to pay a D&D invoice issued late? Under the rule, invoices must be issued within 30 calendar days of when charges were last incurred. An invoice issued after that deadline does not have to be paid.

What evidence wins a D&D dispute? Time-stamped proof that the container could not be moved or returned: appointment unavailability, terminal closure or gate restriction notices, empty-return location changes, and the communications showing your team tried.

The bottom line

Record import volume and new congestion highs mean D&D invoices will follow in volume. The FMC rule gives billed parties real dispute rights and hard 30-day clocks, but those rights only matter if the evidence can be assembled fast.

Capture evidence while the congestion is happening, check every invoice against free time and the event record on arrival, and draft disputes well inside the window. The teams that do this in hours instead of weeks stop paying charges they never owed.

Debales deploys AI agents for drayage coordination, invoice reconciliation and evidence-backed D&D disputes filed inside the deadline. Book a demo.