We recommend following the steps in this order to assist you with finding the username for your Microsoft account.
Check products or services
If you weren't able to find your username in Step 1: You forgot your Microsoft account username by using the lookup feature, try searching other Microsoft products or services that you know are associated with the username.
How to find your Microsoft account username in the product or service you use
For the protection of your account, we have strict policies on how our advocates can help you with your account. Microsoft Support advocates are unable to provide account information without proper validation, but there are places you can look within the products themselves.
Have you ever set up an alternate email address for the account you want to sign in, such as @outlook.com, @gmail.com, or @live.com? If so, try that.
From a Windows 10 device where you’re already signed in, select Start > Settings > Accounts . Under Email & app accounts, you'll see the usernames associated with your device.
Also see Change or reset your Windows password.
Xbox gamertag: Because gamers are identified by their gamertag within Xbox, it’s not uncommon to forget that you created an email address when you signed up for Xbox. For details of where to look on your console, see the Find your Microsoft email address walkthrough.
Microsoft 365 or Office 2016 or newer: Open an Office app, like Word or Excel. Select File > Account. Under Product Information, you'll see Belongs to with the associated username.
Check your email accounts to see if you have any mails or receipts from Microsoft for purchases such as digital games, movie rentals or subscriptions.
If you weren't able to find your username...
If you still couldn't find your username by checking the products or services above, move on to the next step to determine if your account may be closed.