The invoices and credit notes use a form designed in the Specification Designer program. The GST that is printing on your Credit Note will therefore be represented on the specification by a field which has been chosen from the Specification Code 'List'.

It could be that you have the wrong specification code inserted for the GST. Check your tax 'jurisdiction' information to find out which jurisdiction is used for your GST calculation - this is the one that should be inserted in the area you are expecting to see the correct GST printed on your CN.

Regards