Remove the App Cleanly
Removing the app takes two steps in this order: run Prepare for Uninstall on the setup page, then uninstall the extension with Delete Extension Data turned on. The first step matters, because it is the app that knows which vendor bank accounts and services came from it — and that knowledge leaves with it.
If you only want to know what would happen, use Uninstall Impact, which reports the same list and changes nothing.
See the impact first
Choose the 
Search icon, enter E-Invoice Platform Setup, choose the related link, then choose Uninstall Impact.
This is a read-only answer to "what happens if we remove this again", so it is as useful before you buy as before you leave. If the app has written nothing into standard tables, it tells you that:
This app has written nothing into standard Business Central tables, so uninstalling it with Delete Extension Data turned on leaves nothing behind.
Remove what the app wrote
- On E-Invoice Platform Setup, choose Prepare for Uninstall.
- Read the list. It names vendor bank accounts created from an approved supplier document, any Preferred Bank Account Code pointing at one, registered Peppol identities, the e-document services on this integration and their job queue entries, and the stored API secret.
- Confirm.
- Choose the Search icon, enter Extension Management, select E-Invoice Platform, and uninstall it with Delete Extension Data turned on.
Leave that toggle off and the app's own data lingers until you clear it from Delete Orphaned Extension Data.
Uninstalling with the toggle on removes the app's own tables and the Peppol Endpoint fields it added to customers and vendors.
What Business Central may refuse
Some things cannot be removed, and the app reports rather than forces them.
Bank accounts with posted entries against them. Business Central refuses, which is the right answer — remove them by hand if you are sure.
A service an active workflow still references. Delete or disable that workflow first, then run Prepare for Uninstall again, or remove the service by hand.
What stays behind on purpose
Your e-document setup, permanently. The e-document service and the documents it received are yours, not the app's — they would exist for any connector. An e-document that has already been processed and is connected to a purchase document cannot be deleted at all, and a service that has processed documents cannot be removed either. So this is not a "clean it up afterwards" item: once an environment has received e-documents, that history stays, and only rebuilding the environment clears it.
After the app is gone, the service keeps an integration value that no longer resolves. The UI shows it blank; the API returns the raw number.
Corrected master data. Where Get Official Data filled in a name, address or VAT number on a customer or vendor, those are standard fields and the previous values were never stored, so they cannot be put back. The report says so explicitly.
Units of measure created by Add Missing Units. They cost nothing, other documents may now depend on them, and Business Central refuses to delete a unit that posted lines reference.
Documents already exchanged over Peppol, which live on the platform rather than in Business Central and are untouched either way.
What was measured, not assumed
On a real uninstall the app's own tables, its Peppol endpoint fields and its job queue entries all went, and nothing of it appeared on Delete Orphaned Extension Data.
Evaluating the app
If you are evaluating rather than leaving, the useful order is: run Uninstall Impact before you start, so you know what a trial will write into standard tables, and again before you decide. The list is short by design — the app was built to be removable without leaving a mess, which matters most to somebody who has not committed yet.