Hi there unpatel,
It's important that all your transactions be entered correctly so your books can be well balanced. QuickBooks Online is a great tool able to help you keep track of sales and expenses so you can see the profitability of your company. i can provide some information about backups in QuickBooks Online.
As stated in this article, there is a feature to back up the company and restore it in the QuickBooks Online Advanced plan. For other subscription levels, like 4Gal mentioned, there might be some apps made by third-party developers available to back up your company. You can view the apps available to connect with QuickBooks Online by going to the apps tab of your account. Another option would be to go in the affected transaction and change it to the correct tax code.
If you have any other questions, feel free to reach out here.
