Demurrage and detention in foreign trade: the complete guide

The CFO who gets an R$80,000 demurrage invoice in March wasn’t surprised by the port: they were surprised by the lack of information. The container sat idle. The free time expired. The team found out when the cost had already piled up.

Demurrage isn’t bad luck. It’s the predictable result of an operation that doesn’t monitor free time in real time. And detention isn’t an unavoidable fee: it’s what happens when the equipment return has no owner and no deadline visible on the platform.

Before you go on: this guide is for those who pay demurrage, meaning importers, exporters and manufacturers that need to control free time and reduce this cost. FollowNet One is e.Mix’s platform for that profile.

If you are a freight forwarder or logistics operator and need to charge demurrage to your customers, controlling each customer’s periods, generating billing reports and invoicing, e.Mix’s tool for that side of the operation is DemurrageNet.

FollowNet One is e.Mix’s foreign trade software: it centralizes free time control, expiration alerts and demurrage history so the importer’s team acts before, not after. This guide explains what demurrage and detention are, how to calculate them, how to dispute them and how to set up an operation that stops being surprised by these costs.

• → The problem: free time expires without an alert, and the cost shows up on the invoice, not on the dashboard
• → The cost and risk: invisible accumulated demurrage, detention from late returns, emergency freight as a consequence
• → The mechanism: free time control per shipment + expiration alerts + an owner for the return
• → How to start: map the trade lanes with the highest demurrage history and activate free time alerts in less than 30 days

What demurrage and detention are in foreign trade

Demurrage is the fee the ocean carrier charges when the container stays at the port terminal beyond the contracted free time. Detention is the fee charged when the container, full or empty, stays outside the terminal beyond the agreed return deadline.

The two costs have different origins but the same operational root: no real-time control of deadlines.

Free time is the grace period granted by the ocean carrier before charging demurrage or detention. Each carrier sets different periods by route, usually between 5 and 14 days. The most common mistake is treating free time as a guaranteed period without monitoring when it starts counting after berthing.

Why demurrage is an information problem, not an operational one

Teams that rack up demurrage on a recurring basis rarely have a capacity problem. The problem is that the information about free time expiring doesn’t arrive while there’s still time to act.

The typical flow of a reactive operation: the vessel berths, the free time starts running, the analyst waits for the forwarder to confirm the DTA (Brazil’s customs transit declaration), books the truck, and finds out the free time expired two days before pickup. The cost was generated while the shipment sat in an email queue.

Three structural failures feed this cycle:

1. Free time isn’t in the system; it’s in the analyst’s memory. Each shipment has a different deadline by carrier and route. Without a centralized record, control depends on individual attention.
2. The alert arrives after expiration. The demurrage invoice is the first “alert” most operations get. By then, the cost has already been generated.
3. There’s no owner for the return. The full container has an owner. The empty container often doesn’t, and it sits idle until someone notices.

How to calculate demurrage and detention

The calculation follows a logic of progressive daily rates. Carriers usually split the period into tiers: the first days have a lower rate, and the following tiers escalate.

Base formula:

• Days in demurrage = pickup date − (date available at the terminal + contracted free time)
• Cost = sum of the daily rates by tier × number of containers

Practical example: the carrier grants 7 days of free time. The container is available on March 1. Free time expires on March 8. Pickup happens on March 12. Days in demurrage: 4. Rates: days 1–3 at USD 50/day, days 4+ at USD 100/day. Total cost: (3 × 50) + (1 × 100) = USD 250 per container.

In practice, the calculation is more complex: holidays may or may not count depending on the contract; calendar days vs. business days vary by carrier; exchange rate adjustments come into the final conversion. That’s why a dispute always starts by reviewing the free time contract.

How to dispute a demurrage charge

Not every demurrage invoice is legitimate. Calculation errors, free time not applied and demurrage caused by factors not attributable to the importer are grounds for a formal dispute.

Four situations you can dispute:

1. 1. Wrong start date: the carrier counts from berthing, but the correct date is when the container became available at the terminal.
   2. Free time not applied: the contract provides a longer period than the one used in the calculation.

1. Cause not attributable to the importer: demurrage generated by a red channel inspection, scanner unavailability or a documented port strike.
2. Calculation error: daily rates applied incorrectly, tiers swapped, wrong number of containers.

To dispute successfully, you need an auditable trail: berthing date, availability date, DTA date, booking date and actual exit date, all with documentary evidence. Without a record, the dispute has no basis.

Proof from the field: from ignored free time to a predictable operation

Before: The team looked for information manually and dealt with problems late: the demurrage cost showed up on the invoice, not on the dashboard.

After: Alerts now point to where the effort should go, the team acts before free time expires and avoidable demurrage stops showing up.

Eloi Filho, Customs Clearance Director, LOX Shipping
Video (in Portuguese): https://www.youtube.com/watch?v=X21pnGZIyqg&t=333s

The 3 pillars of an operation with zero demurrage surprises

1. Free time centralized per shipment

Each import shipment needs its free time recorded on the platform as soon as the B/L is issued. The record includes the carrier, number of containers, contracted free time and the date counting starts. With that data centralized, the system automatically calculates the expiration for each shipment, without depending on spreadsheets or the analyst’s memory.

2. Expiration alerts with configurable lead time

The ideal alert arrives 72 hours in advance: enough time to schedule the pickup, mobilize the carrier and confirm the DTA. A 24-hour alert still allows action in simple cases. An alert on the expiration day only documents the problem.

Effective alerts are configured by trade lane: critical raw materials get an alert 96 hours ahead; administrative spare parts, 48 hours ahead. The logic isn’t “everything is the same”; it’s “each operation gets the level of urgency it deserves”.

3. A return owner with a visible deadline

The empty container needs an owner and a deadline on the platform from the moment it’s picked up. Green within the deadline, yellow with 48 hours left, red when it has expired. Without a defined owner, the alert becomes noise.

How demurrage control works inside FollowNet One

FollowNet One is built with free time control as a core feature, not as an extra field. Each registered shipment has its free time configured based on the carrier and the trade lane, and the system automatically calculates the expiration.

The concrete operational result: the analyst doesn’t need to remember when each shipment’s free time expires. The dashboard shows, by traffic light, which containers are within the deadline, which need attention and which require immediate action. The manager walks into the S&OP meeting knowing the accumulated potential cost of the shipments at risk, without having to ask anyone.

How to set up demurrage control without an endless project

Owner: Foreign Trade Manager or Coordinator, responsible for making sure every active shipment has its free time recorded and a return owner defined on the platform.

Cadence: daily, reviewing the free time dashboard before the workday starts; weekly, reviewing containers with a pending return and no movement for more than 48 hours.

Demurrage KPI: number of demurrage occurrences without a prior alert, with a target of zero. Any demurrage generated without a configured alert is a process failure, not an operational one.

First scope: the carrier or trade lane with the highest historical demurrage cost in the last 12 months. Register the active shipments, configure the free time and activate the alerts. Visible results in the first month.

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