Hi JW_G,
Thank you for the post. As much as we would like to provide you the information, but we cannot advise on what are the tax implicated your employee would have if they decided to add another 6% of their super salary sacrifice. It would be best to reach out to your accountant for more information. For future reference, you may check the Help Article: Set up salary sacrifice superannuation (myob.com).
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Should you require additional assistance, don't hesitate to respond. We also encourage you to connect with our online help center, MOCA through this link: MYOB Support - MYOB Support, for prompt support.
Kind regards,
Sai