Welcome to the Community family. I can help you revert back to manual sales tax.
There's just a few steps to follow to get back on the manual sales tax feature:
In the left navigation bar, go to Taxes.
Select Sale Tax.
Click Sales tax settings in the upper right corner.
At the bottom of the screen, you'll see "Want to temporarily switch to the old tax center? Switch here."
Click the here link.
For brand new QuickBooks account with automated sales tax enabled, you can use the override capability available on the transactions to ignore the automated calculation. If this won't work and you still want to be removed from auto sales tax, I suggest contacting our QuickBooks Online Care Team.