Thanks for joining the thread, Hesh95!
Using the Split option when categorising your transactions in QuickBooks Online, you can assign a GST code per line for the transaction that needs tax. Then, you can set the other split transaction to Out of scope GST code. Out of scope tax code does not calculate GST on the transaction.
You can check this link to learn more about Find and categorise transactions in QuickBooks.
If the issue persist, I would recommend contacting our Customer Care Team. That way, they can check your transaction and help you categorise them in a secure form.
Please let me know if you have any additional questions. I'm always willing to assist.
