Haha. Typical hmrc.
Basically you have to account for the vat on the invoices not yet paid and the vat on purchases not yet paid on the final vat return. So you can use the adjustment boxes to add the vat from those invoices. Then submit the final return. When those invoices and purchases after have been paid you’ll need to reduce the p and l by the amount of vat again as to not claim it twice. I haven’t had to do this on quickfile before so maybe someone else can advise. But here’s some guidance on whats required.