I made an error mapping the spreadsheet fields to QBO fields and now it shows that I have double charged HST. How can I fix this. Can I delete the entire .csv file?

Welcome to the QuickBooks Community, queenofredhats-g.

You can simply make the necessary changes on the spreadsheet and import it back to QuickBooks. You'll receive a pop-up message stating it will override the previously uploaded transactions. Once you've received this message, you can go ahead and click on "Yes/Confirm". I hope this helps!

Don't hesitate to reach back out if you have any other questions.