KiwiSaver is a voluntary savings scheme offered by IR.
In short, it helps you prepare for retirement by collecting a portion of your income as a contribution every time you're paid.
This happens at source, so once you're enrolled, all contributions are applied by your employer through wage deductions according to
the rate you pick.
By default, the contribution rate is 3%, but you can also choose to contribute 4%, 6%, 8%, or 10% of your income.