Tax rate changes for MacBusiness Payroll for 1 April 2018 have been announced:
From next month (March) you can go to Setup, click the "Tax/ACC/KiwiSaver tab", and click "Update Tax Rates" to load these new rates. The new tax rates won't be applied until you load a pay with a payment date in April. Alternatively, you can wait till you get a prompt from Payroll to update them automatically when you load your first pay with a payment date in April.