Per diem, Latin for per day, is the daily charge for using a carrier’s container or a chassis beyond the allowed free time. In United States practice it usually means the same thing as detention: the equipment left the terminal and was not returned in time, so each extra day is billed.
The term appears in two closely related places. Ocean carriers use it for container detention after gate-out, and chassis providers use it for daily chassis rental beyond an included period. Both are per-unit, per-day charges defined by tariff or lease.
Because per diem, detention, and demurrage get mixed up in conversation, invoices should be read against the trigger events: what equipment, which clock, which start and stop events. In US trades, the framing of these charges has drawn regulatory attention, and invoices generally must identify the basis of the charge.
The events that decide a per diem invoice are the ones tracking captures: gate-out, empty return, and the days between. Keeping those timestamps per container in TrackingMCP gives you the evidence to reconcile or dispute a bill, and the free-time pages show how many days were included to begin with.
Free days, daily rates, and billing rules vary by carrier, terminal, port, and contract. Treat this page as orientation and confirm specifics against your own agreement and the applicable tariff before acting on an invoice.
Per diem, Latin for per day, is the daily charge for using a carrier’s container or a chassis beyond the allowed free time. In United States practice it usually means the same thing as detention: the equipment left the terminal and was not returned in time, so each extra day is billed.
In most US container contexts, yes: per diem is the daily detention charge for equipment kept out of the terminal beyond free time. Chassis per diem is a separate daily charge for the chassis itself.
The chassis owner: a leasing pool, an intermodal equipment provider, or occasionally the carrier. It is billed to whoever signed the interchange, usually the trucker, and passed along commercially.
Detention free time by carrier →
Track equipment events per container →
More in Charges & free time: Demurrage · Detention · Demurrage & detention · Demurrage vs detention vs storage · Free time · Last free day (LFD) · Terminal handling charge (THC) · General rate increase (GRI) · Peak season surcharge (PSS) · Bunker adjustment factor (BAF) · Currency adjustment factor (CAF) · War risk surcharge (WRS) · Browse all 106 terms →