Hi, Richard.
You need to delete the VAT refund from the Taxes page, then recreate the transactions using the correct date. I'll guide you on how.
- Sign in to your QuickBooks Online (QBO) account.
- Click on Taxes at the left pane, then select VAT.
- Go to the Payments section, then look for the VAT refund.

- Select on Delete under Action.
- Click Yes to confirm the action.

After that, the transaction will now appear in the Returns section. From there, re-enter the refund using the correct date.
- Choose the transaction, then tap on Record refund under Action.

- Fill in the correct information including the date and amount.

- Hit Save.
Once done, you're now able to change the date of the VAT refund.
For more tips about recording VAT payment or refund in QBO, you can open this article: Record a VAT payment or refund [Video].
You can also learn more about filing taxes through this link: File your VAT return and record tax payment in QuickBooks Online.
If you have any other questions while updating the date on your VAT refund, let me know by adding a comment below. I'm more than happy to help. Have a good one!