I recognize the importance of adding the correct sales tax in your Go payment app, @Infinite1. Let me provide ways to help you set it up successfully.

As per checking, you can set up sales tax in your Go payment app. Here's how:

1. Open the Go Payment app.
2. Tap the Plus (+) and select New Sale.
3. Select Amount and enter the total sale amount. Choose a Payment method.
4. Click the Taxable option to charge sales tax or tap Add.
5. Then, proceed to charge.

Check this article for detailed steps: Process payments in the Go Payment app.

On the other hand, for assistance with changing the sales tax rate directly in the Go Payment app. I recommend contacting our Technical Support Team. I understand you've already reached them for help. Yet, they have the tools to access your account and can provide screen sharing in a secure environment.

1. Sign in to your QuickBooks Online company.
2. Select Help at the top right.
3. Select or type Contact Us.
4. Enter a brief description of your concern.
5. Choose a way to connect with us: Start a chat or Have us call you.

Intuit doesn't cover additional tax payments. However, you can customize your sales tax in QuickBooks Online, apply it to the customer's invoice for an accurate rate, and pay using the Go payment app. See the screenshot below for reference:

I've included a helpful resource for you: QuickBooks Payments FAQ. This FAQ covers common questions and troubleshooting steps related to credit card payments in QuickBooks.

Keep us posted if you have other questions about managing payment. I'll be around to find ways to help. Stay well.