Time Machine completed a verification of your backups. To improve reliability, Time Machine must create a new backup for you.

10 days to go before the end of 2017, and this problem appears to have been resolved (for me, anyway) by disabling PowerNap.

I know it seems too good to be true, but I would never assume that Apple would have fixed it by now if that was the source of the problem. Who knows how long their bug list is and how it is prioritized. If I recall correctly, though, it was an Apple employee in one of these threads that suggested it could be PowerNap related.

I have several other Macs on the same network, using the same drive for backups, that have never had the problem. But since I tried the disabling PowerNap on the Mac that was having the problem (repeatedly!) it has never recurred.

No new drive. No more reformatting. All I can say is disabling PowerNap (only on the Macbook having the problem) appears to have solved it.

Hi, No need to go into great detail but suffice to say I tried sorting it myself, called Apple Support twice over a 10 month period, all with no success in resolving the issue.

Finally I just turned off 'Automatic Backups' & resorted to manual backups, my choice as to how often I do said backup, which really is no big deal in the scheme of things.

Guess what, for me personally no further problems at all, 8 months or so now & not one dreaded message that a new backup needs to be created.

It will be interesting to see if this works for others or whether I was just lucky (in some ways) but unlucky in respect of Apple not, publicly, recognising & sorting out this issue a long time ago, shame on you Apple!

I agree with Bryrock. After almost six months having turned off PowerNap on my MacBook Pro late 2013, I also have not seen this problem again (knocking wood). I did the same thing on my wife's iMac, which had the problem twice in the past 18 months, and no recurrence there either. Seems like this is the likely culprit and highly recommend those with this problem to turn off PowerNap.

Back up is still good and usable. I just restored a file from it just to verify. But no new backups since Mac "thinks" it's corrupted.

As using a NAS is not supported.......

Apple does not agree with you. You might want to review this Apple Support document:

Backup disks you can use with Time Machine - Apple Support

Time Machine can back up the data on your Mac to these backup disks:

• An external USB, Thunderbolt, or FireWire drive connected to your Mac
• An AirPort Time Capsule's built-in drive (any model)
• An external USB drive connected to an AirPort Time Capsule (any model) or AirPort Extreme (802.11ac model only)
• Network volumes connected using Apple File Protocol (AFP)

Unfortunately though, any kind of network drive.....including the Time Capsule.....is more susceptible to corruption issues than a USB drive connected directly to the Mac.

This is more than 5 years later than the original question. I just got that same message yesterday.

I am running Sierra10.12.6 now with a new MacBook Pro 15" with the USBC ports.

I had been running Yosemite with my older 2010 MacBook Pro 17". The time capsule had backups since Snow Leopard. And I did use it to restore files several times.

I never got that message before but did have other problems with my backup so I erased the time capsule and started from scratch when I got the new MBP 15 in January. The backup file had been working ok until yesterday. I looked at the backup file and there was nothing in it at all. So I did let time capsule create a brand new backup. It took 14 hours directly connected to the time capsule with a cable. But I am not sure I should really trust this new backup.

Hi, No offence meant coocooforcocopuffs but I do not back up multiple machines & never have, my "Message" about needing to create new back up just starting happening.

I do agree though that, thats the way it is, sadly. I'm guessing Apple don't really know what to do about it otherwise we would hear from them publicly

I have had no issues with Synology NAS. Run backups now for over a year. They are certainly not cheap.. so buying a NAS would have to have more justification than simple TM backups. But it is much much faster that TC and is great as file server, as well as media functionality built in.. remote access.. vpn etc etc.

Since Sierra the problem of TIme Machine reliability to any network target is so great that I also recommend using Carbon Copy Cloner.. as well or instead of TM.

FWIW after my fiasco with the Synology NAS, I've had a Drobo 5c connected over USB for about three weeks and am using the same drives in it. Using it exclusively for TM. No problems so far with corruption, though if/when budget permits, I'll probably get a second one as a backup and rotate them. I do recommend that anyone using a RAID solution for TM run Disk Warrior on it at least monthly, whether NAS or not.

I have received the second Time-Machine failure in the past 5 months. Using MBP Late 2013 with 15 inch display and Sierra 10.12.5 (just updated Sierra prior to failure), backing up to a 3TB Time Capsule. I have Power Nap enabled and haven't tried turning it off. Following this chain for a couple of months and not clear from responses whether or not that is a real or imagined cause.

When I got this notice I checked the Time Machine icon on the menu bar and it still showed that the previous backup was being verified. That disappeared when I selected 'back up later.' The later attempt to backup results in re-appearance of the message below.

I don't understand other commenter's mentioning running Disk Utility, as the Time Capsule networked drive does no appear there. I recall from previous research that the Time Capsule backup drive cannot be fixed using Disk Utility. Perhaps third-party drives can be.

I tried to follow link to Apple Bug Reporter from dinky2 above, but takes me to an Apple Developer login page where my Apple ID is rejected. I wouldn't mind barraging Apple about this problem but where is the best place to do that?

I suggest everybody having this problem issues a bug report to Apple Bug Reporter

Maybe flooding them with the same message will eventually get them to take some serious action. This problem has been around for years, looking at the numerous reports on the internet. They just don't do anything about it. Apple just won't take the trouble to look at any fora

As far as I can tell there is no fix for this, it will always happen when backing up multiple machines over several years. That’s the way it just works.

Apple rarely responds to anything posted in this forum. It's user to user.

This discussion started over four years ago, so the only users that might see it are those who posted here and are still following it (I have no idea why I still am).

See C13. " . . . Time Machine must create a new backup for you." and if that doesn't help, start a new topic.

Thought I would share my issue.

Had a early 2009 24 inch Imac. Linked to time capsule, backups without any issues.

Bought a new Imac , 27inch, 2TB on Dec. 26. Started up machine, it was fine. Downloaded data from time capsule, everything downloaded, good to go. This new machine had El Capitan. It seemed to be doing fine. Then I upgraded to Sierra, and soon after (within a day), started getting prompts about how backups couldnt be completed, if issue continued go to disk utility, and run first aid, and then ultimately recieved the message "Time machine completed a verification.....", just like other posters here.

I contacted apple care, long story short, they had me erase all my data (3 years ) from time capsule and start backing up again.(I did have data stored on a seperate hard drive as well, just in case) Did that, took several hours, and next day, the same thing started happening again.

The interesting thing is that I also have a macbook pro, using El Capitan, and it downloads backups to the same time capsule, without any problems!

Called apple care again, and long story short, they decided it was a problem with the OS (sierra), and did clean installs, resets, etc, and still no success. Ultimately they had me totally erase the hard drive, and at that point they kinda suggested to exchange the new computer for another new one. Apple store is only 5 minutes away for me.

Got a another brand new 27 inch Imac, 2 tb, and was able to get my information on it from the hard drive. This one already had Sierra on it. And soon after that, several issues popped up on trying to backups. First issue was that there was keychain issue(I never use keychain, which also had my email hosed up), some how that issue finally went away, and then the "Time machine completed a verification"......started again.

At that point, I connected another external hard drive and am having backups downloaded to it using time machine. Works perfectly, and at the same time, the Macbook pro is still downloading backups to the time capsule without any issues.

I probably have invested 5 hours with apple care in this, and still no resolution. Guess I will just have to use my workaround. Maybe a future upgrade of Sierra will fix it. At this point, I have no clue on what to proceed on.

I have "solved" this problem a number of times, only to have it come back a week to a month later. I had seen it a few times in the past, but it became a regular occurrence only after I upgraded to Sierra. Until a week or so it was only happening with one of two Time Capsules that we have in the house, but now it has happened with the second one as well. There are other symptoms as well, such as the network machine name on my MacBook changing periodically due to a "duplicate" on the LAN, and various Apple devices disappearing and later reappearing in the Airport Utility. I believe all of these symptoms have been described by others here as well.

Yesterday I installed an old Airport Extreme router between our AT&T Pace DSL modem/router and our LAN to see if that would help, configuring the AT&T box to pass its IP address and traffic through to the Airport Extreme ("DMZplus") to avoid "router behind router" and other issues. All is working as expected, although I realize that that does not mean that the problem is "fixed." While the Airport Extreme is an old model from about 2009, it updated to the latest firmware when reinstalled. For good measure, I also switched from using a non-Apple wireless access point to using our late-model Time Capsule, and I replaced an "iffy" Ethernet cable (it was two shorter cables joined with a coupler) connecting the Apple TV to the LAN with a better quality one.

While I was testing the new configuration, I noticed that my MacBook Pro was frequently losing its LAN connection. I have seen this problem before, and it seemed to be worse after LAN reconfiguration, but it did not appear to be related to the router. At first I thought it might be my unmanaged gigabit switch, which feeds wired Ethernet jacks throughout the house, but then it occurred to me to swap out the (external) Thunderbolt Ethernet adapter on my Mac for my spare. That seems to have fixed the disconnect problem!

Now it seems as though there may have been another explanation for the corruption of my Time Capsule backups, which only happened to my Mac and not another one located elsewhere in the house. It may be an issue of lack of robust error recovery on the part of Time Machine, possibly exacerbated by changes made to the network support (or in Time Machine itself) in Sierra. I believe this was mentioned as a possibility earlier in this thread, and I believe that it is quite possible that it explains what I have been seeing. Time (Machine) will tell...