How to Close your Microsoft Account?
Go to Close your account.
When you’re prompted to sign in to your account, double-check that it’s the account you want to delete.
If not, select Sign in with a different Microsoft account.
Check that the page shows the correct Microsoft account, and then click Next.
Read the list, and select the check boxes to acknowledge you’ve read each item.
In the Select a reason drop-down list, choose the reason you’re closing the account.
Select Mark account for closure.
For more details, visit : office.com/setup