How do you remedy a missed invoice off of submitted VAT return?

I managed to miss importing one of my invoices that VAT needs to be assessed on and I foolhardily submitted the return to HMRC before I realised.

The VAT return was accepted by HMRC but I need to find a way to get the VAT due on this one invoice sent to HMRC.

I've noticed that now that the invoice is imported correctly I can run a VAT return in Clearbooks for the same period and I just get a return for the missing VAT but is it just a case of submitting another return for the same period or will that trash the previous return?

The missing amount is very small so it can go into the next month as per the VAT 'oops I made an error' rules but I wouldn't have the foggiest on how to tell Clearbooks to add that to the next quarters VAT return.

Any advise/input/suggestions?

Thanks!