In QuickBooks Online (QBO), once the VAT feature is enabled, reversing or turning off this option is not available, Sonia.

However, as a workaround, since you registered your company by mistake, you can set the default tax rate selection to either Out of Scope of Tax or No VAT in your account settings. This way, your future transactions will not be subject to any taxes or VAT.

Here's how:

1. On your QBO account, go to the Gear icon at the top.
2. Select Account and settings.
   
3. In the left menu, click Advanced.
4. Go to the Accounting section. 
5. Choose Out of scope of Tax from the Default tax rate selection. 
6. Click Save, then Done.
   

The Out of scope of Tax option is intended for businesses that are not VAT registered. If selected, transactions using this option will not appear in any tax reports within your account.

If you happen to have pending VAT entries or transactions that need to be adjusted or have VAT deleted from each transaction, you just need to manually tag your transactions as Out of scope Tax.

Feel free to reply to this post if you need further assistance.