Demurrage and detention aren't the same thing
Demurrage is charged by the shipping line when your container stays inside the port or terminal beyond its free period — typically just three to seven days at Mombasa depending on the carrier. Detention is different: it's charged once the container has left the port but hasn't yet been returned, empty, to the shipping line's depot.
How much these charges actually cost
Demurrage typically runs from around $13 up to more than $100 per container per day, depending on the shipping line, container size and how long the delay runs — and it compounds daily, so a week's delay can add up fast on a single container.
Free time varies by cargo type
Local cargo typically gets nine to 14 free days for container return (detention) at Mombasa, while cargo in transit to landlocked destinations like Rwanda can receive considerably longer free periods — sometimes 30 to 52 days — recognising the longer road journey inland. Confirm your specific shipping line's free-time allowance for transit cargo before your container arrives, since it varies by carrier.
The most common cause: documentation not ready in time
The single biggest driver of demurrage isn't the transport itself — it's incomplete paperwork discovered after the cargo has already arrived at port. Having your clearing agent lodge the Import Declaration Form through Rwanda's Electronic Single Window before the vessel docks, rather than after, means clearance can begin the moment the container is available rather than waiting for documents to catch up.
Practical steps to stay inside free time
Track your vessel's arrival date and work backwards to have documentation, HS code confirmation and duty payment ready in advance. Choose a clearing agent who proactively monitors your shipment's status rather than waiting for you to ask, and if you're regularly importing, ask your freight forwarder about consolidated container release processes that speed up pickup for repeat shippers.
These charges catch out more importers than almost anything else in the shipping process — and they're almost entirely avoidable with planning.