Some items cannot be flagged as stolen.

This does not work reliably on a stack of multiple items.

Check your inventory for newly stolen item(s).

Activate the container again, then remove the item(s) and exit the container.

Switch back to your inventory, and place item(s) in the container again.

Switch to container's inventory, and remove item(s).

Switch to your inventory, and place item(s) in the container.

Access a container with a red icon i.e., one that would result in theft if you took an item from it.

To mark most non-stolen items as stolen, you need to: Dropping this item, then dropping the other will clear the stolen flag on both.

If you have two stolen items, equipping one item will make the second one appear legitimate.

If you have one non-stolen and one stolen item, alternately equipping the two items repeatedly will clear the stolen flag.

In the case of armor, all pieces should be fully repaired so they have identical statistics. In addition to standard ways of clearing the stolen flag on items, there is a glitch that can be exploited for wearable items, as long as you have more than one of the item. Stolen Flag Glitches Clear Stolen Flags on Items

7.2 Permanent Effects from Duplicated Items.

3 Equipping Items That Have Been Removed From Your Inventory.

2.2 Duplicate Items using the Skull of Corruption.

Oblivion weapon sounds missing