Hi @lauren
Yes, you can delete your data and start fresh if you like. There are more details here: How do I clear my account?
Unless you tick the “Paid in full” box on the receipt hub, it will only create an invoice for it. The invoice is editable unless it’s locked (e.g. by year end or a VAT return). But generally, if you view the invoice, you can edit these details.
If you are creating a payment, the invoice will still be editable, but of course you have the payment linked to it too. On the bank statement view you can edit the date for most transactions (there are a few exceptions like foreign currency transactions), but just simply click on the date and change it. You can do the same with the description too.
Hope that helps! 