Clear Books deals with switching from VAT cash accounting to VAT invoice accounting smartly. If you switch midway through a quarter you have the option of declaring VAT from all unpaid invoices on the last VAT cash accounting return. You also have the option of declaring VAT on payments over the next 6 months (this is the only option if you have submitted your last VAT cash accounting return).
Navigate to Settings > Organisation > Details & Tax
Click on the Tax tab on the box to the left and hit the Manage VAT schemes link.
Fill in details of the new VAT invoicing account scheme.
Below this, select whether you would like to declare VAT on all unpaid invoices on your last cash accounting return or whether you would like to declare VAT on payment over the next six months.
The second option will only be available if you have already submitted your last cash accounting VAT return.
Hit the Add button to complete the switch from VAT cash to invoice accounting.
If you have declared VAT on payment over the next six months, the system will include invoices on the VAT return based on the invoice date for all invoices created on the new VAT invoice accounting scheme. All invoices that were created on the cash accounting scheme will be included on VAT returns based on the payment date of the full amount.