In sections 40 and 45, when you see the word "Corporation", it means more than just one organisation. It includes the main Accident Compensation Corporation, but also other people and groups. These are:

You might deal with an accredited employer. This is a special type of employer that has been approved to handle ACC claims for their workers.

You might also interact with someone who is acting on behalf of ACC. This person is allowed to do things for ACC.

Lastly, "Corporation" can mean someone who provides services to you if you have an ACC claim. This doesn't include people who give you medical treatment. These service providers must be working for ACC or have ACC's permission to help you.