In preparing VAT Return QBO has somehow inserted an exception attached. Both purchase transaction and sales invoice for this transaction are already in the VAT Return.

Hello, @communityoil.

The exception amount title will show up when preparing VAT return if there are transactions already filed to the HMRC and have been deleted/edited. That said, they'll be able to know the changes made on your past transaction/s. For now, I recommend reviewing these transactions.

This article gives you more details about VAT exceptions and reports in QuickBooks Online, you can read it for more information.

If there's anything else I can do for you, please don't hesitate to leave a comment below. I'm a few clicks away to help. Have a good day!