Q: "the last backup could not be completed"

Didn't work for me, keeps saying The last backup couldn't be completed

Works like a charm, thank you very much

Wow, I didn't realize this thread was still alive.  Nothing that I did worked and I finally wound up calling Apple support for help.  They wound up having to open a trouble ticked, assign an engineer and a temporary password to my account and attach a diagnostic routine to my iCloud account to figure out what was wrong.  I never did find out what was wrong but it suddenly started working about 48 hours after they initiated diagnostics.

It has worked fine ever since and I was recently upgraded to the $10.99/year for 20GB plan.

I am ready to broke my iphone 6 plus , i am trying with any kind of method the last 2 weeks to complete backup on iCloud with free space at least 10gb and always the same result (iCloud backup can't complete the last time) . Someone from apple forum must give us a correct answer before we last our data .

This worked perfectly. Thank you! 

I have this problem with a Iphone 4s. I see lot of people say they got it fixed with this answer, however I do NOT see an answer on this whole page. Where is it?

Thank you :)

After following the suggestions offered:

1) Backup to computer, and then turn iCloud backup on.

2) Powered phone via AC outlet (2.1 amps), not computer

3) Reset iPhone

4) Deleted previous iCloud backups

5) Increased iCloud storage

I had no absolutely joy - same message about not completing.

However, after doing all that AND moving away from my office network, connecting to another network and powering the phone via an AC outlet (2.1 amps), iCloud backup worked - finally.

Whether it was the network switch alone or all of the above combined remains to be seen. The next question after enabling the iCloud backup is why can't Apple provide better documentation regarding the problem/solution instead of leaving it to the user community to figure it out?

I was having the same issue: could not back up to either iCloud or iTunes. I tried the suggestions in this and every other thread I came across with no luck. It was pretty frustrating! What finally worked for me was to look at Settings > General > Usage > Manage Storage. In the list of apps, there was one app that I had deleted recently, but it still showed in the list, although with a generic target-looking icon instead of the app's usual icon.

I deleted the app from there, and did a hard reset. After the hard reset (this step is essential), I re-downloaded the offending app from iTunes and tried to back up. It worked right away on both iCloud and iTunes!

After the backup, I was able to delete the app, and backups still work.

Hope this helps someone else!

Looks like this backup failure has re-appear after upgrading to iOS 9. After I upgraded my iPhone 5s to iOS 9 backups to iCloud OTA kept failing. I performed the same solution given here, delete any old backups in iCloud, then try to backup again and it worked just fine.

The first iCloud backup I tried after iOS 9 seemed to take a long time... I got impatient, and did a hard reset. The next time, it was super quick... only about a minute or two! Seems to work fine for me after the fix I posted above, and one hard reset post-iOS 9 installation.

How do you delete the old backups in iCloud?

I have the same problem. Since I upgraded to IOS 9 I can not perform backup from iCloud iPhone . Now I want to delete the last copy and tells me it can not eliminate at this moment..Any solution?

Any ideas for not being able to delete backups from the iCloud Winwos application?  I can't get the storage to load at all...

Reboot/reset your iPhone by holding down the home & sleep/wake buttons at the same time until the Apple logo appears then let go & let the iPhone boot up normally.  You should now be able to delete the last backup.  I've been doing this the past few days though unfortunately I still haven't been able to backup my iPad since updating to iOS 9