Welcome to Community, @Ben W.
I'll share some information about VAT returns. You'll want to run the VAT Detail Report to verify the transactions. This way, you'll be able to check if there's a need to adjust the VAT amount or not.
Here's how:
- Go to Reports.
- In the Find report by name field, enter VAT Detail Report.
- Make sure to change the Report period to All Dates.
- Click Run report.

If you're able to find the difference, you'll want to create an adjustment. Refer to this article for the detailed steps: Create or delete a VAT adjustment.
I'm adding this link if you need help managing taxes. It contains tax topics with articles: Taxes.
Please don't hesitate to reach out if you still have questions or concerns with VAT. I'll be around to help. Take care and have a wonderful day ahead.