Apple One fails to solve issues with multiple Apple IDs
Apple One does include one option for helping users manage multiple Apple IDs for iCloud storage, but doesn't resolve the long-standing problems, and does add to the confusion.

Credit: Apple
Some Apple users have different Apple IDs for their iCloud accounts and their App Store and Services subscriptions. That's because Apple's cloud-based services and its iTunes-related subscriptions were initially separate.
Back in September, Apple employee Chris Espinosa said that Apple One "manages" situations like these. Since the debut of the bundled service on Friday, it appears that it mitigates the issue but doesn't solve it.
During the Apple One sign-up process, users will be prompted with the option to associate their included Apple One storage with the Apple ID that they currently use for iCloud. That means users will get the amount of storage included with Apple One on their iCloud Apple IDs, and the initial iCloud storage plan will be cancelled (though their data will remain intact). The other bundled Apple One services will be associated with a user's primary iTunes/App Store ID.
Of course, this solution doesn't involve consolidation or merging of accounts. It only does away with one problem of having a separate Apple ID for iCloud and the App Store and iTunes.
Users are also given the option to keep their Apple One iCloud storage associated with their primary iTunes and App Store account. In these cases, the storage for each account will be handled separately.
At least one Twitter user said that they chose to use their iTunes/App Store account for the included Apple One storage. When they did, it auto-cancelled their iCloud Apple ID storage plan. After that, all of the data in that storage reportedly showed up on their Apple One account.
AppleInsider can't verify if this is common, and couldn't reproduce it ourselves. It could simply be a case of a user's device uploading its data to iCloud on a new plan instead of an actual transferal of data from one Apple ID to another.
While the options here will help users with multiple Apple IDs actually sign up for the service, it's far from the easy account merging or consolidation that users have been asking for.
Update: Since publication of this article, AppleInsider was able to confirm through sources within Apple that merging two separate Apple IDs is still not possible.

Credit: Apple
Some Apple users have different Apple IDs for their iCloud accounts and their App Store and Services subscriptions. That's because Apple's cloud-based services and its iTunes-related subscriptions were initially separate.
Back in September, Apple employee Chris Espinosa said that Apple One "manages" situations like these. Since the debut of the bundled service on Friday, it appears that it mitigates the issue but doesn't solve it.
During the Apple One sign-up process, users will be prompted with the option to associate their included Apple One storage with the Apple ID that they currently use for iCloud. That means users will get the amount of storage included with Apple One on their iCloud Apple IDs, and the initial iCloud storage plan will be cancelled (though their data will remain intact). The other bundled Apple One services will be associated with a user's primary iTunes/App Store ID.
Of course, this solution doesn't involve consolidation or merging of accounts. It only does away with one problem of having a separate Apple ID for iCloud and the App Store and iTunes.
Users are also given the option to keep their Apple One iCloud storage associated with their primary iTunes and App Store account. In these cases, the storage for each account will be handled separately.
At least one Twitter user said that they chose to use their iTunes/App Store account for the included Apple One storage. When they did, it auto-cancelled their iCloud Apple ID storage plan. After that, all of the data in that storage reportedly showed up on their Apple One account.
I have the same. When I selected that I wanted to switch to Apple One iCloud storage it auto cancelled my iCloud account storage plan and all the data I had in that storage just showed up on my Apple One account iCloud storage.
-- Phil Kehoe (@orazio1227)
AppleInsider can't verify if this is common, and couldn't reproduce it ourselves. It could simply be a case of a user's device uploading its data to iCloud on a new plan instead of an actual transferal of data from one Apple ID to another.
While the options here will help users with multiple Apple IDs actually sign up for the service, it's far from the easy account merging or consolidation that users have been asking for.
The need to merge Apple IDs is a real thing that should have been fixed a long time ago. https://t.co/1435liE962
-- Scott Edwards (@scotchua)
Update: Since publication of this article, AppleInsider was able to confirm through sources within Apple that merging two separate Apple IDs is still not possible.
Comments
That said, I trust that people have other reasons (either legitimately or due to poor information, etc.) for holding separate accounts in the past and are now stuck with assets in each of them that need to be merged.
I'd be happy to merge my iTunes account into my iCloud account, but Apple won't let you do that, even though both are MY accounts.
One aspect of why Apple is reluctant to merge or let people inherit Apple IDs is contracts. When you buy a physical cd or piece of software you can pass it to your descendants. I am not sure what contacts between customers and Apple and between Apple and the music industry say to this...
I've been locked in an ongoing battle with Apple concerning the multiple Apple ID issue and they refuse to budge an inch. I've spent hours on the phone with Apple Support trying to fix this and they absolutely refuse to do anything. I actually got one "senior" support person who came up with a harebrained scheme to try to make one of my Apple IDs a family member of my other Apple ID. This turned out to a total clusterf*** and I ended up having to restore my account and my family members had to repurchase all of the shared family purchases that they had installed on their devices. Yes, Apple Support's f-up cost me cold hard cash and they don't give a flying f*** about it.
A side effect of having multiple Apple Ids is that you can get caught entering the wrong password in response to a password request because it's not always obvious which account is asking for the password. After too many inadvertent failed attempts - your account is locked. My solution, no matter how obviously stupid, is to use the same password for all of your Apple Ids unless you like living life on the phone with Apple Support. Does this make sense? Hell no, but Apple has inserted a flaming hot poker into an uncomfortable place on your body and anything you can do to reduce the suffering is worth the effort.
Sorry to peel the scab off a long standing dispute that I have with Apple, but their unwillingness to fix a problem that THEY created as a consequence of me having had a MobileMe subscription is something that I will never forgive them for. They didn't have to make this a problem. They could have fixed it years ago, but they didn't. They left me with a half-baked solution and in the case of Apple One, the inability to benefit from a cost-saving opportunity due to the mess that they created and perpetuate.
There are so many things I like about Apple, and I'm a open supporter of Apple, but this is the one thing that I would bring up if I could sit down with Tim Cook for 5 minutes. Just fix this Apple, you own this problem, you own the code, you own the system, you created this skeleton in the closet, and you owe it to your customers to do the right thing for them and fix this once and for all. This is totally inexcusable and senseless bullshit of Apple's own making and to let it fester for years on end is beyond logic and reason.
I guess this extinguishes any enthusiasm I previously had about Apple One.
and now the problem is compounded because I can’t go for the new Apple service packages without significant inconvenience of migrating iCloud.
I think bitching is likely to continue, as well it should. Apple should have sorted this out ages ago.
Apple is screwing over its customers with perpetually bumbled services.
-started an iTunes account with a non Apple email ID
-started a separate iCloud email account when getting iPhone, bc Apple forces this in order to fully use iCloud features
-Apple doesn’t allow merging of iTunes email/ID with iCloud ID to fix this problem
-I believe one time Cook even said something to the effect of ‘keep using separate IDs for now, it will be fixed in the future’ (a reply to customer email I believe). Well, it’s been about 10 gd years since then, and now it’s not just iTunes that is separate from my iCloud, but music (and all my saved preferences), apps, and podcasts.
And if you can’t afford to lose it then why are you storing it in the cloud?
*,** Case in point - the RISIBLE insertions of capitals when moving the cursor to edit stuff - of a piece with the fustercluck of Apple’s ID mess. After 32 years of using Apple products, I am being sorely tried by this and other problems (mostly caused by inane gimmickry) and am reluctantly starting to ponder alternative solutions. Apple appears to lock exclusively onto The Next Big Thing(TM) and drops the ball on QC for existing stuff. Not a good look - or a good anything. Getting fed up.