I've got an update on why you received a VAT submission error while submitting your return, Paul.

Currently, we have an ongoing investigation into the unknown error when submitting VAT returns in QuickBooks Online (QBO). Rest assured that this case is being worked on with utmost urgency.

In keeping with this, I'd recommend contacting our Customer Care team so your account will be added to the list of affected users. This way, you'll receive regular updates on the progress and its fix. To do this, here's how:

1. Sign in to your QuickBooks company.
2. Select the Help (?) menu.
3. Go to the Search tab and select the Contact Us button.
4. Enter a brief description of your concern in the What can we help you with? field and click Continue.
5. Choose a way to connect (Start a chat or Call us).

Once this matter is fixed and you've successfully filed your VAT return, make sure to record your payment in QuickBooks and check your submission status on the HMRC website.

Don't hesitate to drop a comment below if you need help managing your VAT returns. Know that I'm always ready to assist you further. 

Hi,

Have you managed to get this resolved, I am having the same error since yesterday.

Thanks

Hello 9130346749542716, thanks for reaching out to the Community space. The unknown error you are experiencing is something our product engineers are currently investigating(ref-INV-106889); we'll add you to the users affected. We're expecting an update to be made in product to fix this very soon. We'll email you as soon as we have fixed this.