Hi Bill075
Thanks for the update. Apologies for the delayed response.
Changing the GST amount manually is not advisable, this will cause the expected tax total based on the tax code not to reconcile with the actual tax total. You may also check This Help Article Recording a GST-only transaction to provide you with more information and instructions.
Please don't hesitate to post again if you need help in the future.
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Cheers,
Leneth