When all transactions i.e(posting to Quickbooks or posting to store) are completed with an order, you can archive it by clicking on the archive button or the archive link in the actions column. Remember, you cannot move an order back from the archive to the inbox.
The "Archive" orders' tab is used to save orders that have been archived manually or automatically using archive order rules. Click here to view the various order archive rules.
By default orders that are older than 30 days are readily viewable in the archive and any orders that are older than 30 days can be viewed in the order archived orders area.