The most useful alert is not “container delayed”; it identifies the applicable free-time rule, the last verified event, the owner and the next action.
Begin with the commercial definition that actually applies
In broad operational usage, demurrage often refers to time beyond the allowance while cargo or equipment remains at the terminal, while detention often refers to container use beyond free time outside the terminal. Terminology and charging structures are not uniform across every carrier and trade.
Do not encode one global formula and assume it applies everywhere. Store the carrier or terminal rule, location, import or export context, equipment type, free-time basis, calendar treatment, rate tiers and contract reference used for the shipment.
Capture the events that start and stop each clock
A charge estimate is only as reliable as its event history. Keep planned and actual discharge, availability, gate-out, empty return, terminal return and other contract-relevant events separately. Record the source of every actual event.
- Container and equipment identifier
- Terminal, depot and relevant location
- Event code, local timestamp and time zone
- Carrier, terminal, EDI, document or manual source
- Applicable free-time rule and any approved extension
Design alerts around action windows
A useful control queue should distinguish confirmed exposure from data uncertainty. Missing availability or return events need a different action from a known container approaching its last free day.
- Missing source event: verify data before calculating exposure
- Free-time window open: show remaining operational days
- Action threshold reached: assign pickup, return or escalation
- Exposure started: estimate using the applicable tier and currency
- Invoice received: compare billed period, rate and party to the recorded rule
Assign one owner and preserve an evidence pack
Every exposed container needs a responsible role and a next action. The record should retain booking terms, tariff or contract reference, event evidence, communications, approved extensions, invoice lines and dispute notes.
That evidence supports internal review and any external challenge. Legal and billing requirements differ by jurisdiction; for example, the U.S. Federal Maritime Commission maintains specific detention and demurrage billing rules. Always review the governing contract and applicable regulation.
Manage causes, not only total charges
A monthly charge total does not explain what to fix. Segment exposure by cause: late document, customs hold, customer readiness, transport capacity, terminal issue, carrier data gap or empty-return constraint.
Review preventable exposure, time from availability to assignment, empty-return cycle time, disputed amount and recovery from the responsible party. Keep these measures tied to verified shipment events so the team can act on the underlying process.
Sources and further reading
- Federal Maritime Commission — Detention and Demurrage
- FMC — Final Rule on Detention and Demurrage Billing Practices
This guide provides general operational information. Contracts, tariffs and regulatory requirements vary by carrier, route and jurisdiction.
Common questions
Are demurrage and detention definitions the same everywhere?
No. Broad industry usage is helpful, but terminology, free-time calculations and billing structures vary by carrier, terminal, contract, route and jurisdiction. Store and apply the rule governing the specific movement.
Which dates are essential for control?
At minimum, retain the contract-relevant availability or discharge event, gate-out, empty return or terminal return, plus any approved extension. Exact start and stop events depend on the applicable terms.
Should the system calculate charges automatically?
It can estimate exposure when the applicable rule and required events are known. The result should remain traceable to the rule, timestamps, calendar and rate tier, with manual review for exceptions.