Why I create Invoice unable to choose the tax rate in the GST dropdown?

I understand the challenges you're experiencing when you are unable to select the tax rate in the GST dropdown when creating an invoice in QuickBooks Online (QBO), Luluwawa. 

We can perform some troubleshooting steps to fix this. There are times when the browser is full of frequently accessed page resources, which causes some errors or unusual responses. 

Let's start accessing your account using a different or private browser. You can use either of these shortcut keys:

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Microsoft Edge: Ctrl + Shift + P
• Safari: Command + Shift + N

Once logged in, try to select the GST rate. If it works, I recommend clearing your browser's cache. Doing so will remove the historical data and access QuickBooks with a clean slate. You can also switch to a different supported browser.

Additionally, you can visit these articles for more information:

• How do I set up sales GST rates and use them on forms? (International QBO).
• Create new tax rates in QuickBooks Online.

Let me know if you have further questions about adding the GST rate on invoices in QBO. I'm always here to help. Have a great day.