with immediate effect
Beginning right now. With immediate effect, employees will no longer be able to take company computers home without the written permission of a supervisor.
immediate occupancy
Describing a residence that can be inhabited immediately. We have to move out of our current place next week, so we need something for immediate occupancy.
immediate occupancy
[of an apartment or house] ready to be moved into at this moment. This house is for immediate occupancy. You can move in today if you want. The apartment is empty, so that means immediate occupancy.