Why does the VAT control account not go back to zero

The Community has you covered, @Feli. I can share easy steps so you can reduce the balance in your VAT control account in QBO.

In QuickBooks Online (QBO), when you create transactions it goes to the VAT suspense account. Then, when the VAT return marked as filed the amounts will be now moved to the VAT control account. To zero or decrease the balance in the VAT control account you'll need to record a VAT payment. 

Here's how:

1. Go to the Taxes menu and then select VAT.
2. Click Payments, then hit Record Payment.
3. Choose the bank account you've used to pay HMRC.
4. Enter the payment date and amount in the appropriate fields.
5. Add a memo if needed.
6. Tick Save.

For more info about the process, please see this article: Record a VAT payment or refund. 

Also, to have a summary of info for each box on the VAT return, you may pull up the VAT Summary Report. Let me walk you through the process:

1. Go to Taxes.
2. Click the arrow next to Prepare Return.
3. Select View Summary. 

You can always get back here if you have other concerns or questions about your VAT control account in QBO. I'll be here to help you. Stay safe.