If i fill in a box on my vat return wrongly i can't seem to change it?

Let me take care of this query for you, Elliot.

We can make an adjustment to correct your vat return in QuickBooks Online (QBO). Let's go to the Taxes menu and make some changes from there. I'll show you how.

1. Hover to the Taxes menu and select the VAT tab.
2. From the Returns tab, click Prepare return for the period you are submitting for under the ACTION column.
3. Select the Adjust link on the box you want to adjust.
4. Fill in the necessary changes, then click Save.

You can also see this link for more details: Make VAT adjustments in QuickBooks Online.

If you've already filed your return, I suggest contacting our Support team. They have the tools to securely check your account and assist you in making the adjustment. 

I've also collected these resources that you can utilize for guidance. These provide details on how to manage, create a Vat adjustment, and submit your returns flawlessly: 

• Manage VAT payments in QuickBooks Online
• Create or delete a VAT adjustment
• Submit a VAT return in QuickBooks Online

I'm always ready if you have further questions about your returns. You can always leave the details below and I'll answer them for you. Keep safe!