Hi,
Thank you for writing to Microsoft Community Forums.
I understand your concern. The Microsoft Bluetooth mouse does not require a passkey to connect to the computer. If you are prompted for a passkey, select No passkey. If you do not get the No Passkey option, try to enter 0000 as a passkey by using your keyboard and check if the mouse is connected to you system successfully.
For more information, I would suggest you to refer the article to Connect a Bluetooth device that does not have or require a transceiver that contains information which could prove itself useful to you.
Regards,
Aaron Summith
Microsoft Community – Moderator