For iOS applications, you just need to send zipped.app, the same .app generated by Xcode is enough, you do not need to put it in IPA before archiving it.
For Mac OS X applications (Mac App Store), you need to send the PKG generated by the Xcode Organizer Share / Save To Disk ....
Alternatively, you can use the Create and Archive command and send it through the Xcode Organizer window ... as another user indicates.
source share