New Apple ID for a device that has an existing Apple ID

Okay, that makes this a lot easier! It's mainly a case of getting your things onto another device if you wish. You can still set up Family Sharing if you wish, or you'll just have to buy apps and media again. In fact if you do the transfer process the way I outlined earlier the apps will work, they just won't update or re-download.

Make sure you take advantage of iCloud. You don't actually have to have your things "on" any device, so even if she removes your devices from the account you won't lose anything that's in iCloud. you can even get access to some using the online apps to which you can get access by signing into icloud.com

Usually when people say "child" here they mean an 8-year old. I do not automatically assume that but it does make a difference in what needs to be done.

A lot of what you you need to do depends upon the age of the daughter and if she is considered to be a "child" according to Apple. Also a factor who gets to create a new account? Since ownership of purchases cannot be transferred it makes sense for the person who bought the most takes that account.

This can turn into a very complicated and very long answer so it helps to know from the start what I/we do not need to post as possible solutions.

This document explains how to create a new Apple ID (create an Apple Account) --> How to create a new Apple ID - Apple Support

Create an Apple ID for your child - Create an Apple ID for your child - Apple Support

I'm taking this a step at a time (plus doing other things since this is a volunteer web site with people just like you, not official Apple support). I still don't know your daughter's age and what and how you need to this hinges on her being a "child" or not. Children under 13 in most countries cannot have their own ID without it being part of Family Sharing, in which case you need to do that first which means creating your own account as indicated earlier.

One you have your own account, the next stage will be to see if you can transfer things from your old account. Again that will be a detailed process. Merging Apple accounts (IDs) or transferring data is not officially supported, Read the links below for things you may need to do to transfer as much as is possible and to share some others.

Apps and media bought with one ID are permanently associated with that ID. Look into using Family Sharing to continue to be able to use items purchased with one Apple ID with other Apple IDs, and for some data sharing features.

- Family Sharing - What is Family Sharing? - Apple Support

- Set up Family Sharing - Set up Family Sharing - Apple Support

Share folders with iCloud Drive --> Share files and folders in iCloud Drive on iCloud.com - Apple Support

Read How to use Shared Albums in Photos on your iPhone, iPad, and Mac - Apple Support about about how to share photos.

On your device make sure you have signed in with the first account and make sure you have iCloud turned on so everything syncs to the device that will be yours. If you have signed into the first ID on a device then fortunately when you sign out of that ID, do not erase the device, then sign in with a different ID, it asks you in most cases if you wish to merge the data from the two IDs on your device. Say yes and later delete individual items from the other ID that you do not want. Note, in How to save apps and progress on one Appl… - Apple Community a Community Specialist says, "you will not be able to transfer the meta data from one Apple ID to another. Once you switch to another Apple ID the information associated with the old Apple ID will be gone except for physical content on the device like photos and videos."

Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac --> Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac - Apple Support

If another Apple ID is signed in you may need to enter the password for that ID to sign out of that ID first.

Click on this link to learn how to 'Sign in with your Apple ID' --> Sign in with your Apple ID - Apple Support

Additional community member posts:

- Apr. 2018 post by ASC helper Winston Churchill on transferring data from one Apple ID to another. Can I merge two iCloud accounts - Apple Community

- Feb. 2021 tips from Eric Root Apple ID - Apple Community

You will need to log into your new account on the iMac. Make sure you sign out before your daughter changes the password on the account. Pay particular notice to Find My.

How to turn off Find My on your Mac

1. Choose the Apple menu  > System Settings (or System Preferences).

2. Click your name (or Apple ID).

3. Click iCloud, scroll down, then click Find My Mac (or click Options next to Find My Mac).

4. Click Turn Off.

However, I believe if she removes the iMac permanently from her devices list this should remove Find My too. This is a little bit like what is being described for a new owner in this article though you obviously do not wish to do it all: What to do before you sell, give away, or trade in your iPhone or iPad - Apple Support

You may wish to read the articles 'Two-factor authentication for Apple ID' ( Two-factor authentication for Apple ID - Apple Support ) and 'Get a verification code and sign in with two-factor authentication' ( Get a verification code and sign in with two-factor authentication - Apple Support ). Various sections contain information that is useful in understanding about the trusted devices (an iPhone, iPad, or Mac that Apple knows is yours) system, and how to get a verification code on a trusted device or at a telephone number.