Few line items make an importer’s blood pressure spike like demurrage and detention. They sound interchangeable, they both mean “you’re paying for time,” and they can both snowball from a few hundred dollars into five figures on a single container. But they are different charges, triggered at different points, and you avoid them in different ways.
Here’s the plain-English breakdown — and the operational habits that keep both off your invoice.
Demurrage vs. Detention: The Short Answer
- Demurrage is charged when your loaded container sits inside the terminal past its free time waiting to be picked up.
- Detention (often called per diem) is charged when you keep the carrier’s container outside the terminal too long — the box got picked up, but the empty wasn’t returned within free days.
Memory hook: demurrage = the box is stuck at the port; detention = the box is stuck with you.
How Demurrage Works
When a container is discharged from the vessel, the clock starts on your free time at the terminal — commonly 3–5 working days at U.S. ports. If the container isn’t picked up before free time expires, the terminal or ocean carrier bills demurrage for every additional day. Rates typically start around $75–$150 per container per day and escalate in tiers — by the second week you can be paying $300+ per day, per box.
Common causes: customs holds and exams, missing or late paperwork, freight not paid to the ocean carrier, chassis shortages, and simply failing to dispatch a drayage carrier in time.
How Detention (Per Diem) Works
Once the container leaves the terminal, a second clock starts: the ocean carrier wants its equipment back. You usually get 3–5 free days to strip the container and return the empty. Keep it longer and detention accrues — commonly $85–$150 per day, escalating with time.
Common causes: warehouse congestion or missed unloading appointments, containers used as temporary storage, empty return restrictions at the terminal (the return location won’t accept your empty), and chassis logistics.
There’s Also a Third Charge: Truck Detention
Don’t confuse ocean detention with driver/truck detention — the charge a motor carrier bills when its driver waits at a shipper or receiver beyond free time (usually two hours). If you’re moving port freight, you can be exposed to all three in one move: demurrage at the terminal, per diem on the container, and detention on the truck. Time literally is money at every leg.
What These Charges Look Like in 2026
Post-pandemic regulatory pressure (including the U.S. FMC’s crackdown on unreasonable detention and demurrage billing) forced carriers to clean up their invoicing — bills must now clearly identify the charge, the free time, and the billed party, and importers have a defined dispute path. But the charges themselves remain very real, and at busy gateways like PortMiami, Savannah, and LA/Long Beach, a one-week paperwork delay can still cost more than the drayage itself.
How to Avoid Demurrage
- Pre-clear customs. File entry documentation before vessel arrival so the container is releasable the day it discharges.
- Dispatch drayage early. Book your dray carrier before the vessel berths, not after the container hits the yard. In-bond moves need their paperwork lined up too — we walked through the 7512 process in our in-bond cargo episode.
- Watch the last free day like a hawk. Track it per container, not per shipment — boxes from the same vessel can have different clocks.
- Escalate exams immediately. A customs exam doesn’t always pause the clock; know your carrier’s policy and request extensions in writing.
How to Avoid Detention
- Schedule unloading before pickup. The warehouse appointment should exist before the container leaves the terminal.
- Never use containers as storage. If you need buffer space, transload into a warehouse and return the box — a day of warehousing is cheaper than a week of per diem.
- Confirm empty return locations daily. Return restrictions change; your dray carrier should verify where the empty can go before the truck rolls.
- Work with a dray partner that owns chassis. Chassis availability is the hidden driver of both charges.
Much of this comes down to who’s running your drayage. We put together a full cost-control playbook in How to Cut Drayage Costs in 2026 and a vetting checklist in How to Choose a 3PL Partner in Miami.
Disputing Unfair Charges
Keep gate tickets, appointment confirmations, terminal screenshots, and empty return receipts. If the terminal was closed, refused the empty, or had no chassis available during your “free” days, document it — those are exactly the situations where invoices get reversed on dispute. Dispute in writing, quickly; most carriers have 30-day windows.
The Bottom Line
Demurrage is port storage you didn’t plan; detention is equipment rental you didn’t intend. Both are avoidable with the same three habits: paperwork before arrival, appointments before pickup, and a drayage partner with chassis and daily visibility on free time. Manage the clocks and the money stays yours.
Moving containers through South Florida? Subscribe to The Freight Guru podcast for port-side lessons from PortMiami — and when you need drayage with chassis and a bonded warehouse behind it, our family at Go Freight and Go Warehouse is built for exactly this.
