ITEM/FILE DELETION
Items are retained for 93 days from the time you delete them from their original location. They stay in the site Recycle Bin(first-stage Recycle Bin) the entire time, unless someone deletes them from there or empties that Recycle Bin. In that case, the items go to the site collection Recycle Bin(second-stage Recycle Bin), where they stay for the remainder of the 93 days unless:
- The site collection Recycle Bin exceeds its quota and starts purging
the oldest items
- The items are manually deleted by the site collection administrator
from the site collection Recycle Bin
For info about doing this, see Delete items from the site collection Recycle Bin
SITE COLLECTION DELETION
If an entire site collection is deleted it will remain in the SharePoint Online Administration Center Recycle Bin for 93 days, after which time it will be permanently deleted.
The SharePoint Online site's administrator can access this recycle bin in order to view the deleted site collections therein, as well as the days left on each of their retention periods.