Error Code: 40901, cant use my phone number for signing up

The Microsoft 365 Developer Program only allows one developer program account per phone number. Deleting the old developer profile does not immediately free the phone number for reuse.

From the program rules:

• Only one Microsoft 365 Developer Program account can be associated with a single phone number.
• To use the same phone number with a different account, the existing Developer Program account must be deleted first, and even then a new subscription can only be obtained after the previous subscription has been active for more than 60 days.

In addition, if the phone number is still associated with a personal Microsoft account as a sign-in alias or security info, it must be removed or transferred before it can be used with another account.

Recommended steps:

1. Confirm the old personal Microsoft account no longer uses the phone number:
   • Go to Manage how you sign in to Microsoft / account aliases for that personal account.
   • Under Account alias, remove the phone number if it is still listed.
   • If the phone number is the primary alias, follow the documented steps to change the primary alias first, then remove the number.
2. If the phone number is still tied to another Microsoft account as a sign-in alias:
   • Sign in to the account that currently has the phone number.
   • Remove the phone number from that account.
   • Then sign in to the professional account and add the phone number there.
3. If the Microsoft 365 Developer Program portal still reports that the phone number is in use after the above:
   • The phone number may still be locked to the previous Developer Program record due to the one-number-per-program-account rule and timing constraints.
   • In that case, either:
     • Use a different mobile number to sign up for the Developer Program with the professional account, or
     • Contact Microsoft support for assistance with the Developer Program sign-up if the number must be reused.

Because the program enforces the one-phone-number limit at the service level, the quickest practical workaround is usually to use a different phone number for the new professional Developer Program enrollment.

References:

• Microsoft 365 Developer Program FAQ
• I received a "This phone number has already been taken" message
• Help with "phone number is already used" in a Microsoft account
• How do I change or remove my phone number in Skype?