MFA Security Issues

How to Stop Microsoft Authenticator Codes Going to an Old Phone Number

Olivia Miller Oct 12, 2026 870 views

Question details

The user needs to prevent multi-factor authentication codes from being sent to an outdated phone number after altering their Microsoft Authenticator app setup.

How to Stop Microsoft Authenticator Codes Going to an Old Phone Number

Product: Microsoft Entra
Device & OS: not provided
Scenario: Attempting to sign in to an Azure or Microsoft Entra account after removing the account from the Microsoft Authenticator app.
Observed behavior: Sign-in requests continue to send multi-factor authentication codes to an outdated phone method that is still stored on the account backend.

Before you start

You will need to contact your organization's IT support team or Authentication Administrator, as they require administrative access to the Microsoft Entra admin center to reset your authentication methods.

Solution 1Recommended

Reset Authentication Methods via Microsoft Entra Admin Center

Ask your IT administrator to revoke old sessions and force a re-registration of your multi-factor authentication (MFA).

Because the old phone number is stored on the Microsoft Entra backend, simply deleting the app on your end will not remove the outdated phone method. An administrator must clear the old data so you can register a new device.

Access Microsoft Entra Admin Center

Have your Authentication Administrator log in to the Microsoft Entra admin center.

Locate the User Account

Navigate to 'Users', click on 'All users', and select the specific user account experiencing the authentication issue.

Manage Authentication Methods

Click on 'Authentication methods' in the left-hand menu to review the stored verification options for the account.

Remove and Revoke

Delete the obsolete phone method from the list, then click 'Revoke multifactor authentication sessions' to clear any lingering logins.

Require Re-registration

Click 'Require multifactor authentication re-registration'. The next time the user signs in, they will be prompted to set up Microsoft Authenticator again with their correct device.

Reset Authentication Methods via Microsoft Entra Admin Center

Setup Completion: Once the admin completes these steps, you will be able to bind your new phone number or device to the account during your next login attempt.

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Frequently Asked Questions

Why is Microsoft Authenticator still using my old phone number after I deleted the app?

Even if you remove the account from the Microsoft Authenticator app on your personal device, the Microsoft Entra backend retains your old phone number as a default fallback method. An administrator must manually remove it from the system.

Can I change my authentication phone number without an administrator?

If you still have access to your account using another approved MFA method, you can usually update your security information at mysignins.microsoft.com. However, if you are completely locked out and codes are going to an old number, only an Authentication Administrator can reset it for you.

What happens when an admin requires MFA re-registration?

The next time you attempt to sign in to your Microsoft or Azure account, the system will prompt you to set up your security information from scratch. This allows you to safely register your new device or new phone number with Microsoft Authenticator.

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