Detention vs. demurrage: what is the actual difference?
The two terms are often used loosely, but they refer to different charges. Demurrage is typically charged when a container stays within the port or terminal beyond its agreed free time before being gated out. Detention is typically charged when a container is held outside the port, at a consignee’s premises or elsewhere, beyond its agreed free time before being returned empty.
Both are effectively a cost for holding onto a container longer than agreed, but they are tracked against different locations and different free-time clocks, which is exactly why manual tracking gets complicated fast.
Why manual tariff tracking is risky
Detention tariffs are rarely one-size-fits-all. They can vary by principal, by port, by city and by time period, and the free-time clock starts the moment a container is unloaded, not when someone happens to notice it. Tracking all of that by hand across even a modest container fleet makes it very easy for a deadline to slip past unnoticed.
The cost of that slip is not abstract. A missed detention deadline either means charges going uninvoiced, or a container sitting with a customer far longer than intended while nobody follows up.
What automatic detention calculation looks like
A dedicated system applies the correct tariff automatically based on the container’s principal, port, city and the relevant period, calculating detention directly from its unload and return dates. That removes the manual lookup step entirely, and it means advance and final detention invoices can be raised with or without a pre-set tariff, as the situation requires.
Security deposits and refunds
Security deposits add another layer that is easy to lose track of manually: deposits collected, adjustments applied, and refund requisitions raised once a container is returned in good order. Keeping this tied to the same container record as detention charges makes it far easier to see, at a glance, what is still outstanding and what is ready to be closed out.
Bringing it into one system
None of this needs to live in a separate spreadsheet from the rest of your container operations. When detention, security deposits and container inventory sit in the same system, follow-up stops depending on someone remembering to check, and starts happening because the dates and tariffs are already there.