At the moment, you'll have to update each tax rate on your product and service items manually, as there's no option to do this in batches within the program. I understand how convenient it would be for you to have a faster way to do this. Therefore, I'll make a note of this as a suggestion to enhance your experience in QuickBooks.
Furthermore, I recommend sending feedback to our developers. They can review your request and likely include it in future updates. Here's how:
Select Settings and click Feedback.
Enter your comments or product suggestions. Then, select Next to submit feedback.
To change your tax rates, simply follow these steps:
Go to Sales and select Product & services.
Click the Edit button on the item you want to update.
Choose your tax rate in the GST drop-down list.
Select Save and close.
For additional reference in handling your items in QuickBooks, you can check out these articles: