This can vary from person to person, and project to project.
Some clients are willing to come up with a plan and design on their own and some prefer to have the builder do all this for them. This can be a good idea especially with renovation work as if you do not have the vision and experience required it can actually lead to a lot of stress and put you in a negative frame of mind before anything is achieved.
The majority of building and renovation work will require a consent, although there are certain types of “exempt” work that can be carried out without council consent if completed by a licensed building practitioner.
Certain projects are classed as “restricted” - for these, you will need a LBP to complete the work. Work involving the building structure, weather tightness require a competent builder to complete. A record of work (ROW) can only be completed by a licensed builder and this paperwork gets lodged on the council files.
The answer is no, but it is highly recommended.
By using a member of CBANZ (Certified Builders of New Zealand) you will be sure they are trade-qualified and have suitable references and are always up-skilling to keep on top of their trade.