When an sales invoice that has already been included on a VAT return is deleted, no reversing entry is made on the next open VAT return, meaning the client is not refunded the VAT that has been incorrectly paid.
Need to either update the system so the VAT returns pick up these deleted invoices, or the system should block the user from deleting an invoice that is already reconciled for VAT, with a pop-up prompting the user to post a credit note instead.
I assume the same applies for purchase invoices, but so far I have not encountered that scenario so is untested.
I agree with Bruce's comment. Whilst a lock can be put in place to prevent any invoice/purchase been deleted, it would be useful to prompt client's so that they are reminded to create a credit note.