How can you submit a VAT return prior to signing up with Quickbooks?

Hello, sbemery. 

You'll want to submit prior VAT returns in QBO. You can set up the VAT as the effective date to pull up the return. Then mark it as filed so you'll have the option to enter your VAT payment.  

1. Go to Taxes, then select VAT.
2. Select Prepare return to view your open return.
3. Confirm the dates and figures are correct. When you are ready to submit your VAT return to HMRC, select File online with HMRC.
4. Select Submit a VAT Return/Set up a VAT Direct Debit Instruction, then select Submit a return. Copy the amounts from your QuickBooks Online return to the HMRC webpage.
5. Once you're done, go back to QuickBooks Online and select Mark as Filed. 

Once you mark your VAT period as filed, QuickBooks Online creates a journal moving the amount of VAT due from the VAT Control account to the VAT Suspense. Then, to protect the information from being changed, you can close your books to protect your past transactions. Please check this article for reference. Close Your Books To Lock Past Transactions.

Let me know if you have other questions about your VAT or need additional help. I'll be right here to assist you. Have a wonderful day!