Events are stored per module. A Novated Settlement document loaded against a driver on the Fleet Events Tab doesn't appear on the same person's Events Tab in Salary Packaging. So the same file gets saved twice, once in each module, and the two copies can drift.
In scope
Events Tab in Fleet and Events Tab in Salary Packaging showing a shared set of events for the same underlying person
Attached documents (Novated Settlement docs and the rest) visible from both
Creating, editing and deleting an event from either module, with the change reflected in the other
Out of scope (for now, worth confirming)
Migrating or de-duplicating historical events that already exist in both modules
Any change to event types themselves
Functional requirements
Linking. The two modules need a reliable way to know that the Fleet driver and the Salary Packaging employee are the same person. If there's already a shared person ID, use it. If the link is looser than that, this is the first thing to nail down, because everything else depends on it.
Display. Both Events Tabs read from the same source. Same events, same attachments, same order. Where an event is only meaningful in one module, it should still be visible in the other rather than hidden, unless we decide otherwise on event type.
Write behaviour. An event created in either module writes once and appears in both. Same for edits and deletions. No copying between modules.
Permissions. This is the one to think hardest about. Salary Packaging users and Fleet users don't necessarily have the same access rights, and settlement documents can be commercially sensitive. Options are: show everything to everyone who can see the Events Tab, filter by event type, or filter by existing module permissions. Needs a decision before build.
Validation and audit
Standard Catch-e confirmation prompts on save and delete
Audit trail records which module the event was created or changed in, and by whom
Deleting from one module deletes from both, so the confirmation prompt should make that obvious
Acceptance criteria
A Novated Settlement document loaded in Fleet is visible on the same person's Events Tab in Salary Packaging without being re-saved
The reverse also works
Edits and deletions in one module show in the other
No duplicate records created
Permissions behave the way we decide above, and are tested for both user types