If your building is accessible to the public in any way and you wish for them to access it prior to your building work being approved as complete then you need to apply for a Certificate for Public Use.
In order to apply for a CPU you must have already been granted a building consent but not yet received a CCC. Public use areas are areas that are easily accessible to the public, whether they pay to enter or not. Places like shopping malls, cinemas, restaurants, schools, hospitals, churches, clubrooms etc.
Please note that if you have a building that is predominately not open to the public (eg. entry by key pad or swipe card) but there is a reception area that is open to the public then you will need a CPU. Private homes and apartments do not require a CPU. Building Compliance and Land Development can assess your requirements and handle the documentation aspect of this.