Glad to hear from you again. I'll be happy to share more info on changing your sales tax rate in QBO.
If your business requires a custom sales tax rate, the following article will show you how to make changes to it as necessary.
Note:Changes to the tax rate will apply to any future transactions you add it to. If you need to change the tax rate for an existing transaction, open that transaction and edit the rate manually.
For additional information, check out: What do I need to do when a tax rate changes?
In case you have other questions, feel free to contact our support team using this link here.