Unless you have a contract which states that you will pay ESCT on top of you employer contributions, then you do not need to.
Your employee is receiving less in their KiwiSaver account because of the ESCT deduction, but there is no obligation for you to take on an additional cost to make up for it. You are still contributing the amount required, and complying with your obligations.
A superannuation contribution must be at least 3% of the employee’s salary or wages.
In most cases, no. The employer contribution remains the same, but the employee will receive less in their KiwiSaver account because the tax comes out of the employer’s contribution. There is no new cost imposed on the employer.
The only exception to this is if the employer has contractually agreed to pay the ESCT on top of the Employer Contribution. In this case, a cost is incurred by the employer.