We can certainly try and help in terms of using QuickFile, but any accounting or bookkeeping queries will need to be run past your own accountant or bookkeeper I’m afraid.
It’s worth noting that invoices have to be at least 6 months old before they can be marked as a bad debt in your account. At this point, a “Bad Debt” button will appear on the invoice itself and QuickFile will log this for you.
What’s on the invoice at the moment preventing you from amending the date? For example, is it locked due to a VAT return or year end journal?
If you have cancelled the bad debt, the modify button should appear for you to amend the invoice date as normal, providing the invoice itself isn’t locked in another way.