Change VAT Scheme


I incorrectly set my profile up as Flat Rate Invoice Based when it should have been Standard Scheme. Each quarter-end I've used adjustments to correct the vat return as I had allocated payments / receipts and was unable to change scheme. I have now submitted my latest vat return, have no transactions after that date and have no allocated receipts or payments. The system will still not let me change the VAT scheme to Standard, with the error message that I must submit a vat return. I've just submitted a vat return so I'm confused about what I need to do to make the change.