Demurrage vs. Detention: Definitions, Charges, and How to Dispute

You’ve seen the line item. Maybe it said “demurrage.” Maybe it said “detention.” Maybe it said both, lumped together, with a dollar figure that ruined your afternoon. Somewhere between pulling the invoice and pulling up your email, you asked the question every shipper eventually asks: What’s the difference, and why am I paying for it?

The confusion between demurrage versus detention costs real money. Demurrage hits when your container sits too long at the terminal. Detention hits when you hold the carrier’s equipment past free time. Two different clocks. Two different parties. Two different line items that often land on the same invoice with zero explanation. And for years, your only option was to pay up and move on.

However, the FMC has since changed that. Tighter billing and dispute rules now give shippers clearer ground to push back on charges that don’t add up, and we’re going to give you a practical breakdown of how to do so: what each charge means, how the clocks start ticking, and how to dispute the ones that won’t survive scrutiny.

What Demurrage and Detention Mean

The industry throws these terms around loosely, sometimes interchangeably. But when a billing dispute heats up, the difference comes down to three things: what asset is being charged for, when free time started, and whether the charge served its intended purpose. Under current FMC rules, both demurrage and detention cover charges tied to terminal space or containers, not the freight itself.

Demurrage: The Terminal Clock

Demurrage is the fee for occupying terminal space. Your import cargo sits past free time, and the meter starts running. But the charge only holds weight if the cargo was genuinely available for pickup and free time gave you a reasonable window to retrieve it. The FMC has been clear: demurrage exists to promote freight fluidity, not to generate revenue from delays shippers didn’t create. Terminal closures, unavailable cargo, and blocked appointment slots all qualify as legitimate dispute grounds.

Detention: The Equipment Clock

Detention is the fee for holding the container itself, often listed as per diem. You keep the box past the allowed return window, and charges start stacking. But detention falls apart when returning the empty wasn’t realistically possible. The FMC has flagged several scenarios as likely unreasonable: return locations that changed without notice, terminals that refused empties, or windows too narrow to meet.

How the Charges Work (and Where They Break Down)

The fight over demurrage and detention rarely centers on whether a carrier can charge you. It centers on whether the invoice was compliant, timely, and tied to what happened on the ground. FMC rules require specific invoice fields, a 30-day issuance window after charges stop accruing, and at least 30 days for you to seek mitigation or a refund.

Demurrage Charges

Demurrage kicks in after terminal free time expires, but the invoice has to earn its keep. Before you pay, confirm it includes the following. Otherwise, a missing field can make the entire invoice defective:

• Bill of lading and container number
• Port of discharge and container availability date
• Free time dates and specific dates charged
• Rate basis and dispute contact details

Beyond paperwork, be sure to also ask the harder questions: 

• Was the container available? 
• Did free time start before you could realistically pick it up? 
• Were appointments open? 

The FMC has said demurrage should incentivize movement, not punish importers for conditions outside their control.

Detention Charges

Detention invoices look simpler but unravel fast under scrutiny. The core dispute questions are operational:

• Was the return location communicated clearly?
• Did the terminal accept empties?
• Was a dual move required?
• Did a usable appointment window exist?

One current note worth flagging: most of Part 541 remains in force as of March 2026, including invoice and timing rules, even after a 2025 court decision removed § 541.4. 

So, focus less on broad legal arguments and more on hard invoice defects, timing failures, and factual proof that the charge didn’t serve its purpose.

How to Dispute Demurrage vs. Detention Charges

You’ve got the definitions. You know what should be on the invoice. Now what? You pick a fight with the billing party, and you win it with paper. Not outrage, not phone calls where someone puts you on hold for 40 minutes. Paper. Timestamps, screenshots, appointment denials, terminal notices. The FMC gives you 30 days to request a refund, mitigation, or waiver, and the billing party gets 30 days to respond. Use that time to build something airtight.

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• Audit the Invoice Before You Argue the Facts: Grab the invoice and check it against what Part 541 requires: BOL, container number, port of discharge, free time dates, availability date, specific charge dates, rate basis, and dispute contact. If any of those fields are missing, you may not owe the charge at all.  
• Build a Real Timeline of What Happened: Pull together every receipt, screenshot, appointment denial, and terminal notice you can find. Map out the shipment day by day: discharge, availability, gate closures, pickup attempts, and empty return instructions. The FMC cares deeply about whether you had a fair shot to move or return that box. Give them the proof.
• Match Your Facts to the FMC’s Incentive Principle: “We shouldn’t have to pay this” won’t cut it. Show that demurrage cargo wasn’t available or that terminal access was blocked. Show that detention equipment couldn’t be returned because the location changed late or the terminal refused empties. That language mirrors how the FMC thinks, and it lands harder than asking for a courtesy waiver.
• Submit Fast and Ask for Something Specific: Don’t send a vague “we dispute this” email on day 29. Use the billing party’s stated dispute channel, name the relief you want (full waiver, partial mitigation, refund), and attach your evidence with a clear summary of which rule or fact supports you. Make the reviewer’s job easy.
• Escalate Smart if the First Round Goes Nowhere: The FMC’s charge complaint process covers shippers, consignees, truckers, and third parties invoiced by a common carrier. You’ll need the carrier ID, an explanation of the Shipping Act violation, and supporting docs. Two catches: complaints don’t reach back before June 16, 2022, and they generally skip MTO charges unless a common carrier was behind them.

Stop Paying for Someone Else’s Problem

Every demurrage or detention charge has a story behind it. A broker who didn’t have HTS codes ready. A trucker who showed up to a closed gate. An empty return location that changed overnight with zero notice. Some of those situations were preventable. Others weren’t your fault at all. Either way, the answer starts upstream: sync customs, drayage, terminal activity, and warehousing early enough that cargo keeps moving, and keep the receipts for when it doesn’t.

That kind of coordination is hard to pull off with five different vendors who don’t talk to each other. Mallory Alexander has spent over a century building the opposite: a customs brokerage that feeds directly into transportation planning, ocean freight, and drayage under one roof, more than 2 million square feet of U.S. warehouse space across 31 locations, and a visibility portal (myMALLORY) that tracks shipments, milestones, documents, and customs entries in real time. When a demurrage or detention charge does land, you’ve already got the documentation to fight it.

We’re here for you. Contact Mallory Alexander to learn more about reducing demurrage and detention exposure, improving documentation, and building a cleaner dispute process before the next invoice shows up.