How to dispute a demurrage invoice: build the case, not the argument
Most disputes fail for the same reason. They open with a complaint about the amount instead of a recalculation of it.
Start from the assumption that the invoice can be wrong
Carrier billing systems compute D&D charges from the data they hold. When that data is incomplete or a tariff version is misapplied, the invoice is wrong in good faith. Nobody is being dishonest; a system produced a figure from imperfect inputs.
The practical implication is that paying without checking is a policy decision, not a neutral default. It is a decision to accept whatever the system produced.
Rebuild the calculation from the container's own timeline
A dispute is only as strong as the recalculation behind it. Six inputs are needed, and all six must come from your own records rather than from the invoice:
- Discharge date, which starts the demurrage clock.
- Gate-out date, which ends demurrage and starts detention.
- Empty return date, which ends detention.
- Container type, since size and reefer status act as multipliers.
- Free time allowance that applied under the contract in force, not the published standard.
- The tariff grid version in effect on each accrual date, which is where most errors hide.
Recompute from those six. Where your figure differs from the invoice, you now hold both numbers and the arithmetic between them.
The discrepancies worth raising
Not every difference is a winnable dispute. These four are, because each is verifiable against a document rather than a recollection:
- Wrong tariff version. The carrier revised its grid mid-year and applied the current one to an earlier accrual. This is the single most common error and the easiest to evidence.
- Wrong free time. The published allowance was used instead of the one your contract negotiated. Your contract settles it.
- Wrong trigger date. The charge runs from a date that does not match the terminal's own records for discharge or gate-out.
- Calendar treatment. The grid excludes Sundays or public holidays and the calculation counted them, or the reverse.
Conversely, arguing that a delay was caused by congestion, by customs, or by circumstances outside your control is rarely productive. Those are commercial conversations about goodwill, not billing errors, and mixing the two weakens the parts of your case that are actually provable.
How to present it
Send the recalculation, not the objection. In practice that means a single document containing the container number, the six inputs with their supporting evidence, your computed figure, the invoiced figure, and the difference. No narrative about how difficult the month has been.
This works because it moves the burden. A carrier receiving a complaint has to decide whether to make a concession. A carrier receiving a recalculation has to identify which of your six inputs is wrong. Those are very different conversations, and only one of them tends to resolve.
Why this is a systems problem, not a diligence problem
Any competent team can audit one invoice. The difficulty is auditing every invoice, every month, across hundreds of containers, while the underlying tariff grids keep changing. Done manually, teams end up spot-checking the largest invoices and paying the rest, which is exactly the distribution in which small systematic errors survive.
Recomputing automatically at the point the invoice arrives is what turns the audit from an occasional exercise into a control. That is the function of a demurrage and detention system: not to argue with carriers, but to make sure that every figure you pay has been checked once.