Hi James,
Once you have selected the relevant VAT return, if you scroll all the way to the bottom, there is an option to delete, please see below:
Subsequently, when you rerun the VAT return, it should pick up the invoices and bills under cash accounting. However, there is another issue at hand, when changing the schemes, the system would not update those invoices to cash accounting. Usually, on invoice accounting, the system would debit/ credit VAT control, but on cash accounting, it would debit/ credit VAT cash control, but once paid, the system would post a journal to VAT control.
For this particular situation, those invoices/ bills have affected VAT control but are picked up on the invoice date rather than payment date. Unfortunately, there isn't much you can do. On the other hand, you are able to correct the unpaid invoices once the correct VAT scheme is set up, you will have to manually click Edit and Update the unpaid invoices.
Thanks,
Tommy