I'll help you change the GST rate in QuickBooks Online, @AZ2.

Modifying the GST rate requires manual intervention, along with updating your recurring transaction in QuickBooks. Before we proceed, please take note of the reminders below:

• The transactions that were made using the previous rate will stay the same unless you modify the transaction and explicitly choose a different GST rate.
• When using recurring templates that include the modified component, any new transactions created with the template will use the updated rate. Previously created transactions will not be affected.
• The updated rate will apply to new transactions entered after the effective date.
• If you enter a new transaction dated before the Effective date, the transaction will be processed using the previous rate.
• If you initiate a new transaction while using past dates, the transaction will be processed at the current rate.

Here's how to modify the GST tax rate:

1. Go to Taxes.
2. Choose the Edit GST dropdown, then select Edit rates.
3. In the tax rate table, choose the rate you want to change and select Edit.
4. Note: You will not be able to edit any QuickBooks Online default tax rates.
5. In the Edit tax rate window, change the rate. You can also change the name if you like.
6. Set the Effective date, if required, this will be the date from which the rate change will take effect, and choose Save.
7. Select On or Off beside the tax rate you want to make active or inactive.

Here is an article for more details: Edit GST rate in QuickBooks Online.

For future reference, you can read this article to guide you in customizing invoices in QuickBooks Online: Customise invoices, estimates, and sales receipts in QuickBooks Online.

Let me know if you have questions about modifying the GST rate in QuickBooks Online. I'm always here to help. Have a great day.