Great to hear from you, osl-ltd.
When voiding an invoice, all payments associated with it will be cancelled. Then, the transaction will not impact your reports or account balances, and you have a record of it.
Also, the VAT in the voided invoice will not include in the VAT return. This means it will take off automatically from the collected Sales VAT total. If the sales invoice was in a previous return in QuickBooks, it will create an exception on the current return to adjust it.
For more details about voiding sales transactions, you can check out this article: Void or delete transactions in QuickBooks Online (QBO).
If you need to adjust your current VAT account to correct on the prior returns, just refer to this article for the steps and details: Adjust your VAT liability.
I've got a link here where you can find articles about managing VAT into your account: https://quickbooks.intuit.com/learn-support/vat/misc/02/uk-vat?label=QuickBooks%20Online.
Feel free to reply to this post if you need a hand with filing VAT returns or any QBO related. I'm glad to help.
