A takedown date records when a unit's creative came down. Together with the posted date it evidences the full run, which is what completes a campaign's record.
Your account can set these directly.
Setting Them In Bulk
Bulk takedown dates are set from the three dots menu, not from an Actions button. This is the single most common reason people cannot find the option.
Open the campaign and go to Creatives → POPs.
Select the units.
Open the three dots menu.
Set the takedown date.
*Note: If you are looking for this under an Actions menu, you will not find it. It is the three dots.
Why They Are Worth Recording
Completing the campaign record. Posted and takedown dates together show the actual run, which may differ from what was booked.
Evidencing delivery. A client querying whether a unit ran for its full flight is answered by these two dates.
Spotting short runs. A takedown earlier than the booked end date is worth investigating, and may warrant a conversation with the media owner.
Seeing Them Across A Campaign
Add Posted Date and Take Down Date to your campaign grid columns. Side by side against the booked start and end dates, discrepancies are obvious immediately.
There is also a Marked as Still Live at column, which records when a unit was last confirmed as running — useful on long campaigns where you are checking in periodically.
**Note: Do this before the campaign closes out and gets reported on. Reconstructing takedown dates weeks later means relying on someone's memory, and the record is only as good as when it was captured.