I have adjusted box 6 in my tax return and it has added it to my total. Please can you let me know how I remove this

Hello there, @joanna6. 

Welcome to the Community. Let me show you the steps on how you can remove the item you have adjusted in box 6. Here's how: 

1. Click the Accounting tab in the left menu. 
2. Go to the Bank register or account where the adjustment was posted.
3. Click View register under the ACTION column.
4. Select the item to open the transaction.
5. Click More at the bottom of the screen, then choose Delete. 
6. Select Yes to confirm that you want to delete the item.

For more information, you can also read through our help article: How to delete a transaction. It also contains a short clip that can guide you through deleting a transaction in QuickBooks Online. 

Feel free to post again for your other concerns. We're all delighted to help you anytime.