How do i add old sale invoices that dont fall into my vat period as ive forgotten a few?

Hello there, @robbie-ross.

Thank you for posting here on the Community page. I'd be glad to help share information about filing VAT in QuickBooks Online (QBO).

If those invoices are dated on the period wherein you've already filed VAT, you can date the transactions/invoices to its original date or modify the date to the current period. Yes, these invoices will be added/reported on the current period as an Exception report.

To learn more about VAT exceptions and reports, you may check this article: VAT exceptions and reports.

You may also check our self-help articles for your reference in the future: Help articles for QBO.

I'll be right here to help you if you have any other questions about filing VAT, just add a comment below. Wishing you the best!