How to manage multiple Apple Accounts on iOS 18?

What exactly happens when you try to log in with the other account? If you see a message it always is a good idea to include it when asking a question here.

Refer to this support article —> View and remove your devices that are associated with your Apple Account for purchases - Apple Support

‘When you try to associate a device that was previously associated, you might notice a message that says, “This device is associated with another Apple Account. You cannot associate this device with another Apple Account for [number] days.” You might need to wait up to 90 days to associate the device with a different Apple Account.’

The above statement is new in 2024. It used to be Apple only talked about restricting app downloads and streaming for 90 days.

Merging multiple Apple ID's or using them simultaneously is not supported I am afraid

I do not have multiple accounts so I can't reproduce what you are seeing. Conceivably it is showing both because you are using one account for the app store and the other for everything else. If you are signed into the same account for both then conceivably if you are still seeing another, it is perhaps detecting the presence of apps from another account? Again, I don't have that on my devices so I am guessing.

The whole system is not designed to accommodate multi-region use. If anything, that could even be read as violating Apple's terms of use, so I suspect trying to do that is made very difficult by Apple. You are trying to do something that devices are not configured to accommodate, so don't be surprised if it is not working.

You can only have one primary email address. That one is your Apple ID that you use when signing in. Apple lets you add other addresses as a rescue address.

Typically you entirely erase a device between signing in with separate accounts. If you do not do that you end up with possibly merging data from the two accounts.

Apple's change from "Apple ID" to "Apple Account" was a change in naming. An Apple ID used to refer to both the email address you used and to the entire account, so that was confusing. Nothing else changed except how things were called.

There is no simple solution to multi-region use of devices. The only one I know of is to buy a second device that you use when you need to use apps from another region. Even then you may have problems in configuring it if you do not have a mailing and billing address in the other country too. You do not necessarily need phone service on the other device if you can make it work over the Internet alone.

I have this same issue. Used to be no problem and I need the banking apps etc from my home country which are not available where I live now plus my music accounts have years of history and I don’t want to lose that but can’t get them on my watch now since I updated to ios18. Ridiculous. Apple should support multiple accounts for exactly this reason.

I can understand the issues, but that is part of life. When I moved to a different country I had to say goodbye to things I liked from the old country and learn to appreciate things the new country had to offer. Also some things involved restrictions that each place did and did not have. I owned things in my old country that my new country did not allow and I could not buy, and likewise my new country has things that were illegal in my old country. Apple has to respect those licensing and distribution boundaries. You need to contact your bank and ask them to make their apps available in other countries. They may or may not see a need for that, just like they may not see a need for setting up a physical branch in the city where you live in your new country.