Microsoft Account Errors

How to Fix Invalid Phone Number Alias Error in Microsoft Account

Khadija Khan Oct 10, 2026 868 views

Question details

The user is unable to add a phone number as an alias to their Microsoft account and receives an 'Invalid Alias' error message.

How to Fix Invalid Phone Number Alias Error in Microsoft Account

Product: Microsoft Account / Microsoft Rewards
Device & OS: not provided
Scenario: Attempting to add a phone number as a sign-in alias for Microsoft Rewards or a standard Microsoft account.
Observed behavior: The system rejects the phone number, displaying an 'Invalid Alias' error, commonly because the number is already associated with another account.

Before you start

Ensure you have physical access to the phone number you are trying to add, and verify whether you might have used this number previously to create an Xbox or secondary Microsoft account.

Solution 1Recommended

Remove the Phone Number from an Existing Microsoft Account

The most common reason a phone number is flagged as an invalid alias is that it is already linked to another Microsoft account. Removing it frees it up for your primary account.

Microsoft only allows a phone number to be actively used as a sign-in alias on one account at a time. If you or a family member used this number previously, you must unlink it first.

Sign in to the alternate account

Go to account.microsoft.com and sign in using the Microsoft account that currently holds the phone number.

Access sign-in management

Navigate to 'Your info' on the top menu, then select 'Manage how you sign in to Microsoft'.

Remove the phone number

Locate the phone number in the list of account aliases and click 'Remove' next to it.

Add to your primary account

Log out, sign back into your primary Microsoft Rewards account, return to the 'Manage how you sign in to Microsoft' page, and select 'Add phone number' to try again.

Remove the Phone Number from an Existing Microsoft Account

Instant Availability: In most cases, the phone number becomes available to be used as a new alias immediately after being removed from the old account.

Solution 2

Use an Alternative Phone Number or Email Alias

If you cannot recover the old account that holds your phone number, you will need to use a different phone number or create a new email alias.

Solution 3

Contact Microsoft Support for Account Synchronization Issues

If you are absolutely certain the number is not linked to another account, there may be a temporary Microsoft service issue preventing alias registration.

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Frequently Asked Questions

Why does Microsoft say my phone number is an invalid alias?

This error most frequently occurs because the phone number is already registered as a primary alias or security information on a different Microsoft account. It can also happen during a temporary Microsoft account service outage.

Does registering my number in the Microsoft Authenticator app make it an alias?

No, simply adding your phone number to the Microsoft Authenticator app for two-factor authentication does not automatically register it as an active sign-in alias for your account.

How long do I have to wait to reuse a removed phone number alias?

Generally, a phone number becomes available immediately after being successfully removed from another Microsoft account. If you still see an error, waiting a few hours for the servers to sync often resolves the issue.

Can I use a VoIP or landline number as a Microsoft account alias?

Microsoft typically requires a valid mobile phone number capable of receiving SMS text messages for alias verification. Virtual numbers (VoIP) or landlines are frequently rejected by the system.

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