How should an importer audit ocean and drayage invoices together?
Key Takeaways
An importer should audit ocean and drayage invoices together by checking each invoice against its own agreed charges, while using one shared container timeline to decide which leg caused any demurrage, detention, or storage. An AI logistics coordinator can keep that timeline for every container and match each invoice line to the leg and event that supports it.
- Ocean freight and drayage are two separate services with separate invoices, terms, and providers.
- Drayage is the short truck move of a container between a port or rail ramp and a warehouse.
- The two invoices should never be merged into one total. Each line belongs to one leg.
- What connects them is the container timeline: arrival, availability, last free day, pickup, delivery, and empty return.
- Demurrage, detention, per diem, and storage charges depend on who held the container and when.
- U.S. rules require ocean carriers' demurrage and detention invoices to include specific details, and missing details can remove the obligation to pay.
- Wilson, by Cartage, is an AI logistics coordinator that coordinates ocean and drayage moves, keeps the container record, and audits each carrier invoice against what was booked.
Why should ocean and drayage invoices be audited together but kept separate?
Ocean and drayage invoices should be audited together because the same container events drive charges on both, but kept separate because each invoice is governed by its own agreement and provider. An AI logistics coordinator should check every line against the right leg's terms and use the shared timeline only to assign responsibility for time-based charges.
Two legs, two sets of terms
| Leg | Typical provider | Typical charges | Agreement that governs it |
|---|---|---|---|
| Ocean | Ocean carrier or NVOCC | Ocean freight, surcharges, terminal handling, demurrage, detention | Ocean rate agreement or quote and the carrier's tariff terms |
| Drayage | Drayage carrier | Line haul, fuel, chassis, pre-pull, storage, waiting time, detention at the warehouse | Drayage rate confirmation or quote |
An NVOCC, or non-vessel-operating common carrier, is a company that arranges ocean shipping without operating ships. A rate confirmation is the document that states the agreed price and terms for one load.
Rail moves add a third leg
Some containers move by rail from the port to an inland ramp before drayage. That adds another provider and another set of dates. The same principle applies: each leg is checked against its own terms, and the shared timeline decides responsibility for time-based charges.
Why merging them causes errors
When a team adds both invoices into one "landed freight" number and compares it with one quote, errors hide. A drayage overcharge can be offset by an ocean line that came in lower. A demurrage charge can be paid twice, once by the ocean carrier and once passed through by the drayage carrier. Separate checks prevent this.
Invoices arrive at different times
Ocean invoices may arrive weeks after the container moved, while drayage invoices often arrive within days. The audit should not wait for both before starting. Each invoice can be checked as it arrives, with the timeline ready for whichever comes first.
What links the two
The container timeline links the legs. The ocean side controls when the container is available and how much free time there is. The drayage side controls when the container is picked up, delivered, and returned. Most disputed charges sit at the boundary between the two.
Who owns each invoice
In many importers, the ocean invoice goes to one person and the drayage invoice to another, sometimes in different departments. Each checks only their own invoice and never sees the other's dates. A shared owner, or an AI logistics coordinator that sees both, closes that gap without merging the invoices.
Freight forwarders and brokers
Some importers use a freight forwarder that arranges both legs and sends one combined invoice. Even then, the lines should be split by leg and checked against each leg's terms. A combined invoice is still two services underneath.
The furniture importer's case
Furniture importers often bring in many containers of bulky goods that need appointments at their warehouses. A slow unloading day can push an empty return past its free time. A late drayage pickup can turn into demurrage. The importer needs to know which leg caused each day of charges, and who should pay.
The cost of not auditing
Time-based charges on containers can grow quickly. A few extra days at the terminal or with the empty can cost more than the drayage move itself. Without a shared timeline, these charges are often paid as billed because nobody can prove they were wrong.
Hypothetical example: one container, two invoices
This example is hypothetical and does not describe a real customer. A furniture importer receives an ocean invoice with $480 of demurrage and a drayage invoice with $300 of chassis charges and $150 of storage for the same container. The team first checks each line against its own terms. Then it uses the container timeline to see that the container was available for three days before the drayage carrier picked it up, which explains the demurrage and points to the drayage schedule.
What should be checked on the ocean invoice?
The ocean invoice should be checked line by line against the ocean rate agreement or quote, the carrier's published terms, and the container's availability and pickup dates. An AI logistics coordinator should flag any line that does not match those records before it is approved.
Ocean invoice checks
| Line | Check against | Common problem |
|---|---|---|
| Ocean freight | Agreed rate for the lane and container size | Wrong container type or old rate |
| Surcharges | Agreed surcharges and validity dates | Surcharges not in the quote |
| Terminal handling | Agreed terms | Charged twice or at the wrong rate |
| Demurrage | Free time, availability date, pickup date | Days counted before availability |
| Detention or per diem | Free time, empty return date | Days counted after the empty was returned |
Demurrage is a charge for a container staying at the port or terminal past its free time. Detention, sometimes called per diem, is a charge for keeping the carrier's container outside the terminal past its free time. Free time is the number of days allowed before these charges start.
U.S. rules for demurrage and detention invoices
Under 46 CFR Part 541, a rule from the Federal Maritime Commission that took effect in 2024, demurrage and detention invoices from ocean carriers, marine terminal operators, and NVOCCs must include specific information. That includes the bill of lading number, the container number, the free time, the start and end of free time, the container availability date, the dates for which charges apply, and the rate rule. The invoice must also give a contact for disputes. The rule says invoices must be issued within 30 calendar days of when charges were last incurred, and missing required information can eliminate the obligation to pay. Importers should check every ocean demurrage and detention invoice for these elements.
Disputes have a deadline
Most carriers and terminals set a time limit for disputing a charge. The team should know those limits and raise disputes inside them. An audit that happens months later may be too late to recover anything, even when the charge was wrong.
Availability is not arrival
A container may arrive at port days before it is available for pickup, for example because of customs holds or terminal congestion. Demurrage should usually be counted from availability, not arrival, under the applicable terms. The availability date is one of the most important facts in the audit.
Check the container number on every line
An invoice line with the wrong container number is a common error, especially when an importer has many containers on one vessel. Each line should be matched to the right container and bill of lading before anything else is checked. A charge on a container the importer never received should be removed.
Surcharges and validity dates
Ocean quotes often list surcharges with validity dates. A surcharge that was valid for one sailing may not apply to another. The audit should compare each surcharge with the quote that covered the actual sailing date.
Free time can differ by agreement
Free time is not the same for every importer. Some agreements give extra free days on certain lanes or for certain volumes. The audit should use the free time in the importer's own agreement, not a general default.
Hypothetical example: missing availability date
This example is hypothetical and does not describe a real customer. An ocean demurrage invoice lists five days of charges but no container availability date. The AI logistics coordinator flags the invoice as missing required information under the federal rule and asks the carrier for a corrected invoice. The carrier reissues it with the availability date, which shows only three chargeable days.
What should be checked on the drayage invoice?
The drayage invoice should be checked against the drayage rate confirmation, the pickup and delivery records, and the empty return record. An AI logistics coordinator should confirm each line is agreed and supported by an event before approval.
Drayage invoice checks
| Line | Check against | Common problem |
|---|---|---|
| Line haul | Rate confirmation for the move | Wrong zone or distance |
| Fuel | Fuel terms on the rate confirmation | Fuel added to an all-in rate |
| Chassis | Chassis terms and days used | More days than the container was out |
| Pre-pull | Request or approval for pre-pull | Pre-pull never requested |
| Storage at the drayage yard | Pre-pull and delivery dates | Storage days that overlap delivery |
| Waiting time at the warehouse | Free time and arrival and departure times | Hours longer than the records show |
| Detention at the warehouse | Delivery and empty pickup dates | Charged when the warehouse unloaded on time |
A chassis is the trailer frame a container sits on for road transport. A pre-pull is when the drayage carrier picks up a container early and stores it at its own yard before delivery.
Port congestion fees
During busy periods, some drayage carriers add congestion or waiting fees at the terminal. These should be in the rate confirmation or approved in writing. If the drayage carrier waited at the terminal, the timeline should show when it arrived and when it left with the container.
Pre-pull and storage need a reason
Pre-pull and yard storage can save demurrage when the warehouse cannot take a container right away. But they should be requested or approved, not added by default. The audit should find the request or approval for each pre-pull.
Rates by zone
Drayage line haul is often priced by zone or distance from the port. A warehouse in a different zone than the one quoted, or a change in delivery address, can change the rate. The audit should check that the zone billed matches the actual delivery address.
Chassis days follow the container
Chassis charges should match the days the container was on the chassis. If the container was delivered and unloaded in one day but the chassis was billed for four, the team should ask why.
Overweight and special equipment
Heavy containers may need a tri-axle chassis or overweight permits, which carry extra charges. These charges are valid only if the container was actually overweight and the equipment was requested or required. The audit should compare them with the container's declared weight.
Waiting time at the warehouse
When the warehouse is slow to unload, the drayage carrier may bill waiting time. The audit should compare the charge with the free time in the rate confirmation and the arrival and departure times at the warehouse.
Dry runs
A dry run happens when the drayage carrier goes to the terminal but cannot pick up the container, for example because it is on hold. Carriers often bill a dry run fee. The audit should check whether the container was actually available at the time and who caused the failed attempt.
Hypothetical example: unrequested pre-pull
This example is hypothetical and does not describe a real customer. A drayage invoice includes a $175 pre-pull and two days of yard storage. The importer's records show the warehouse had an appointment for the day the container became available. No pre-pull was requested. The AI logistics coordinator flags both lines and asks the drayage carrier for the request record. The carrier removes the charges.
How should the shared container timeline be built and used?
The shared container timeline should record each event with its date, time, and source: vessel arrival, availability, last free day, pickup, delivery, unloading, and empty return. An AI logistics coordinator should build it while the container moves, so both invoices can be checked against the same facts.
The container timeline
| Event | Source | Why it matters |
|---|---|---|
| Vessel arrival | Ocean carrier | Starts the port process |
| Container available | Terminal or carrier | Usually starts demurrage free time |
| Last free day | Carrier terms | Last day before demurrage |
| Drayage pickup | Drayage carrier and terminal | Ends demurrage, starts container use |
| Delivery to warehouse | Drayage carrier and warehouse | Starts warehouse time |
| Unloading complete | Warehouse | Ends warehouse waiting |
| Empty return | Drayage carrier and terminal | Usually ends detention or per diem |
The audit workflow
| Step | Trigger | What the AI logistics coordinator does | When a person steps in |
|---|---|---|---|
| 1. Record events | Each container event | Saves the date, time, and source | When sources disagree |
| 2. Match ocean lines | Ocean invoice arrives | Checks each line against ocean terms and the timeline | When a line is not supported |
| 3. Match drayage lines | Drayage invoice arrives | Checks each line against drayage terms and the timeline | When a line is not supported |
| 4. Assign time charges | Demurrage, detention, or storage found | Uses the timeline to show which leg held the container | When responsibility is disputed |
| 5. Request corrections | Unsupported lines | Sends the right provider the evidence | When the provider disputes |
| 6. Record outcome | Each invoice | Saves the decision and reason | Never |
Last free day alerts
The best way to avoid demurrage is to schedule pickup before the last free day. The AI logistics coordinator can watch each container's last free day and alert the team, and the drayage carrier, when pickup is not yet scheduled with enough margin. Prevention is cheaper than any audit.
Assigning responsibility
When demurrage builds because the drayage carrier picked up late, the drayage agreement may decide who pays. When detention builds because the warehouse took days to unload, it may be the importer's cost. When the container was held by customs, neither carrier may be at fault. The timeline makes these questions answerable.
One record per container
All events, invoices, and decisions for a container should live in one record. When a question comes up months later, the team can open that record and see the full story.
Build the timeline as the container moves
Collecting dates after the invoices arrive is slow and often incomplete. Terminals and carriers may no longer show old events. The timeline is most accurate when each event is recorded as it happens, by asking the carrier or checking the terminal on the day.
Keep the sources
Each date should keep its source. A terminal record, a carrier status, and a warehouse log may disagree by hours or days. The audit should use the most reliable source and note it.
Customs holds
When customs places a hold on a container, it may not be available for pickup even after arrival. Charges that build during a customs hold may be treated differently under the importer's agreements. The timeline should record holds and their release dates, so the audit can separate them from carrier or warehouse delays.
Hypothetical example: who caused the detention
This example is hypothetical and does not describe a real customer. An ocean carrier bills four days of detention. The timeline shows the container was delivered on day one, unloaded on day four because of a warehouse backlog, and returned empty on day five. The importer accepts that the detention came from its own warehouse delay, approves the charge, and asks the warehouse to plan appointments better.
How should importers evaluate software for ocean and drayage audit?
Importers should evaluate software with a container that has charges on both invoices: demurrage from a late pickup, an unrequested pre-pull, chassis days that do not match, and detention from a slow unload. An AI logistics coordinator should keep the two invoices separate, use one timeline, and explain each decision.
The evaluation test
| Test case | Pass | Fail |
|---|---|---|
| Demurrage with no availability date | Flagged as missing required information | Paid as billed |
| Late drayage pickup | Demurrage assigned to the pickup delay | Charged without explanation |
| Unrequested pre-pull | Flagged; request asked for | Paid |
| Chassis days mismatch | Corrected to days used | Paid as billed |
| Slow warehouse unload | Detention assigned to the warehouse delay | Disputed without evidence |
| Two invoices | Kept separate with their own terms | Merged into one total |
Use a real container
The best test uses a container the team already knows, with both invoices and the actual dates. The team can then see whether the software reaches the same answer it did by hand, and how much faster.
Include a customs hold
One test container should have had a customs hold. The software should record the hold and its release, and not assign the days during the hold to the drayage carrier.
Questions to ask in a demo
- How does the software record container availability and last free day?
- Does it keep the ocean and drayage invoices separate?
- How does it decide which leg caused a time-based charge?
- Does it check demurrage and detention invoices for the required information?
- How does it ask each provider for corrections?
Measure results
After choosing software, the importer should track demurrage and detention per container, the share of invoices with corrections, and the time from invoice to decision. Falling demurrage and fewer disputes show the process is working.
Warning signs
- One "landed cost" view with no line-level checks.
- No record of container availability or empty return.
- Demurrage and detention paid without a timeline.
- The software cannot tell which provider billed which line.
Teams that want the basics can read about demurrage versus detention in ocean freight, and teams checking a late pickup can see whether the demurrage invoice matches the timeline.
Where does Wilson fit in ocean and drayage invoice audit?
Wilson, by Cartage, is an AI logistics coordinator that coordinates freight across modes, including ocean and drayage, from quote and booking through tracking, delivery, invoice audit, and payment. Wilson keeps the container record with each shipment and audits and reconciles each carrier invoice against what was booked.
Wilson replaces the TMS for freight execution and connects to the company's ERP. A TMS, or transportation management system, is software used to plan, book, and track freight. An ERP, or enterprise resource planning system, is the company's main business system for orders, inventory, and accounting.
Why the timeline matters to Wilson
Because Wilson coordinates the drayage pickup, delivery appointment, and empty return as part of running each container, the dates the audit needs are recorded as the work happens, not reconstructed later from emails.
How Wilson handles the two legs
Wilson works with the customer's approved ocean and drayage providers, tracks each container using the best source available, and checks each invoice line against the right leg's terms and the container timeline. Unsupported lines go back to the provider with the evidence. Wilson works with carriers through email, API, EDI where the carrier supports it, and phone calls where configured.
Approvals stay with the importer
When a charge falls in a gray area, such as a delay that was partly the warehouse's and partly the carrier's, Wilson brings it to the person who owns the decision with the timeline and the terms. It does not decide disputed responsibility on its own.
Payment
Customers use the Wilson Wallet to pay their carriers. Payments above approval limits or outside the rules wait for a person. Wilson has no subscription or platform fee; its pricing is a percentage of the freight payments coordinated through the Wallet. Pricing scales down as volume grows, and Enterprise pricing is custom.
What Wilson does not do
Wilson does not act as a freight forwarder or customs broker, and it does not file customs entries. It coordinates the providers the importer has approved and audits their invoices against what was booked.
What Cartage asks in discovery
Cartage asks how many containers the importer receives, which ocean and drayage providers it uses, how warehouse appointments are set, and how demurrage and detention are reviewed today. These answers shape the container timeline and audit rules an AI logistics coordinator follows.
Part of the wider audit
Ocean and drayage checks follow the same principles as any freight audit: compare each line with what was agreed and what happened. Teams can see the full approach in the freight invoice audit and payment guide.
Where teams start
Wilson starts with assisted execution. Approval limits are set by the customer, and routine actions can run automatically within those rules as reliability is proven. Timing depends on scope: most teams start on a few lanes and expand from there.
FAQs
How should an importer audit ocean and drayage invoices together?
Check each invoice against its own agreed charges, and use one container timeline to assign time-based charges to the right leg. An AI logistics coordinator keeps the timeline and matches every line.
Should ocean and drayage invoices be combined into one total?
No. Combining them hides errors. An AI logistics coordinator keeps each invoice separate with its own terms.
What must a U.S. ocean demurrage invoice include?
Under 46 CFR Part 541, details such as the bill of lading and container numbers, free time and its start and end, the availability date, the charged dates, and the rate rule. An AI logistics coordinator checks for these.
Who pays for detention after a slow warehouse unload?
Often the importer, if the timeline shows the warehouse caused the delay. An AI logistics coordinator shows the reviewer the timeline before a decision.
What is a drayage pre-pull, and should it be paid?
It is an early pickup and yard storage before delivery. It should be paid only when it was requested or approved. An AI logistics coordinator checks for the request before approving the charge.
Sources
- Electronic Code of Federal Regulations, 46 CFR Part 541, "Demurrage and Detention Billing Requirements": https://www.ecfr.gov/current/title-46/chapter-IV/subchapter-B/part-541
- Cartage, Wilson product scope and pricing position, November 2026: https://cartage.ai
Ask Cartage to show how an AI logistics coordinator audits ocean and drayage invoices against one container timeline: talk to the Cartage team.