If you are over 18 and contributing to KiwiSaver from your salary or wages, your employer is required to put in a minimum of 3% of your Before Tax Pay (less employer's superannuation contribution tax).
You can choose to contribute 3%, 4%, 6%, 8% or 10%, however, your employer is still only required to contribute 3%.
The exception to this is if you are on a "Total Remuneration Package". This allows an employer to set a fixed remuneration amount for each employee. If the employee joins KiwiSaver, the cost of the employer contribution comes out of the employee's pay.