For the ops desk, this is the deadline the trucking plan is built backwards from: a container gated in after the CY cut-off is rolled to a later sailing and sits at the port accruing storage charges. It is the physical deadline for the box itself, not to be confused with the SI cut-off, which is the documentation deadline for submitting shipping instructions and typically falls earlier. When haulage runs late, the CY cut-off is what the forwarder checks to decide whether the container can still make its vessel or has to move to the next sailing.
Glossary
CY Cut-off
The latest time a loaded export container can pass through the terminal gate and be accepted into the container yard for its intended vessel, set by the carrier and communicated on the booking confirmation.