Found items cannot be deleted. Every record keeps its full history so you can always prove what happened to an item. Instead, items move through their life cycle:
Extend: if the owner needs more time to collect, change the "Storage until" date of the item.
Expire manually: set "Storage until" to yesterday. The item turns grey and appears in Resubmission.
Archive: once the item has physically left the office, archive it with a reason (returned, donation, police, destroyed, test entry, duplicate …).
Why it matters
Retention periods exist because found property must be kept for a defined time before it can be disposed of. The period is set per category (and optionally per found place) by your administrator. Later, retention rules delete or anonymise old records automatically.
Good to know
A wrong or test entry is archived with the reason "test entry" or "duplicate" – not deleted.
Archived items can be reactivated by users with the right permission.
Expired items in bulk: use a task list or scan list and archive them in one step.