An Apple ID by default employs 2FA I.e. Two-Factor Authentication for iPhone from the time you create one. Now what is 2FA, you may ask. Well, the feature allows a user to verify, access, and recover his/her Apple ID or any account for that matter via an OTP (One Time Password) sent to an assigned and trusted phone number. Simple isn’t it? Now, building upon this, let’s learn how to add trusted phone numbers for Apple ID login to help you access the same in case you get locked out.
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1. How to add trusted phone numbers to access your Apple ID
How to add trusted phone numbers to access your Apple ID
1. Unlock your iPhone and fire up the Settings app.
2. Tap the Apple ID account name (your name).
3. Choose Password & Security.
iPhone home screen 
Settings menu 
Apple ID settings
NOTE: If for some reason Two-Factor Authentication is not active, please enable it first and follow the on-screen instructions. This way you can add your own phone number as the default authentication method along with others in the following steps.
4. Locate and find the TRUSTED PHONE NUMBER section and Tap the Edit button.
5. Select Add a trusted phone number and enter the iPhone passcode to continue.
6. On the next screen, specify a trusted phone number of your choice and then tap the Send button. A verification code/OTP will be sent to the number.
Add trust phone number 
Enter passcode 
Specify trusted number
7. Enter the code you received and it’s all done.
To add more, delete, or change trusted phone numbers to the Apple ID, go back to step 4 through step 7.
Wrapping up
That’s all folks, you have now successfully added a trusted phone number to your Apple ID account for verification purposes. This comes in handy when you have forgotten your account password or device passcode and have just upgraded your iPhone to a newer model.
Thank you all for reading.