Hi, Krisztina. Let me clarify things to help you with backdating your VAT returns in QuickBooks Online (QBO).
When you say "backdated to 2021," are you referring to backdating transactions to claim VAT for your VAT return? If so, QuickBooks allows you to enter transactions from previous years. The same applies when filing VAT returns. If you encounter any unusual behavior, you can log out and log back in to your QBO account.
Here are some helpful resources to better manage your VAT returns in QBO: Getting started with VAT in QuickBooks.
If you’re referring to something else, please don’t hesitate to leave a comment below.