I can give you the steps to update your sales tax rate in QuickBooks Online.
If you're using the Automated Sales tax, we're unable to permanently update the sales tax rates. If you opt to change the rate for future transactions, I highly recommend contacting our phone agents. They have the tools to revert your account to the old sales tax setting so you can add a new rate.
Here's how to contact us:
Go to the Help (?) menu.
Tap the Contactus button.
However, we can also override the rate directly on the transaction. Here's how:
Open the invoice/sales receipt.
Click the Sales tax link below the Subtotal.
On the Let's calculate your tax rate window, click on the Override this amount link.